just need a lil vent!

You can take a redirection order on post for up to 4 years! If you haven’t sorted your post by then I don’t know what to say??‍♀️
Royal Mail say this on their website( as you are right that you are not allowed to open post addressed to someone else)

I've received someone else's mail

If you’ve received mail which has your address, but not your name, this is because we deliver to addresses rather than names. If this does happen, you can put a cross through the address and write 'Not known at this address' or 'No longer lives here' and put it back in a letterbox. Where possible, we’ll return the item to the sender hopefully allowing them to update their records.

If you’ve received a ‘Something for you’ card that’s not in your name, we recommend you dispose of the card and once our retention period has ended we'll return the item to the sender.

If you’ve received mail which isn’t in your name or your address, we're really sorry we've made this mistake and inconvenienced you. We'd like to get the item to the intended recipient as soon as possible and would greatly appreciate your help. Please post the item when you can, you won't need to apply any postage, we’ll then process and deliver it to the correct address.

My daugher and her partner have tried to register on the electoral roll for my address. I only knew when a letter arrived for her from the local council, as I wasn't expecting anything for anyone but myself I opened it.
The local council said the only reason would be for a credit reference company as they like to check the register and the worse part was if, if she had ticked for it to be private in the same way as ex directory I'd never have known. They were very good and have made a note on my address for future reference. Bad debt is not connected to the address, it is the person and bailiffs are much more reasonable than you think so try not to get stressed over this.

After over 15 years in this house I think I've finally stopped getting post for the previous owners but there was nothing untoward - they left a forwarding address and I often see the wife anyway as we are members of the same music society and sing in the same choir so passing things on is no problem.

However we left our forwarding address for the people who bought our old house to use if anything arrived after the redirection ended. Sadly they never used it and I realised I'd lost things when they didn't arrive as expected and I remembered I'd not updated my address for the expected items. I really don't see how difficult it is to forward something, even if it is irritating, and receiving something that way would prompt you to update the sender.

I would be suspicious of a seller who didn't leave a forwarding address as I have always left one - but then I have nothing to hide!

I finally snapped last year when I recieved yet another batch of marketing letters for an old tenant. I marked each and every once in bold red letters - DEAD, REMOVE FROM DATABASE.
Since then? Not one single letter for her.....!

Not as bad as you, but we have had the same thing with our landline number. We have had the number fir 7 years! The previous owner of the number did not live in this house. Recently a local dentist called to say that the lady had left without paying. We don't know where they live now. They may have innocently forgotten to tell people their number has changed, but they seem to be bad payers.

As others have said, sending letters back is what a determined fraudster would do. I once had debt collectors knock at the door of my newly purchased flat, when I showed them the legal paperwork proving that I was now the owner they went away and I heard no more. The people I bought it from had been in a rush to move.......

www.citizensadvice.org.uk/consumer/post/stop-getting-junk-mail/
Not quite what the OP is asking, but may help.
One point is to refer to the Data Protection Act when asking a company to stop sending you mail and to remove your address from their database.

Many years ago, we bought a ground floor maisonette. We were awaken at 2am by hammering on the door.

It was the police looking for the previous owner, the police had the place surrounded. It was a very frightening experience in the middle of the night.

This is such a time wasting irritation fizzers - I do feel for you! At our last house we had a lot of correspondence and calls for the children of the previous owners; they evidently weren't too keen on paying rent for their homes and I think Mum and ?Dad had stood guarantor. At this house I have lost track of the number of calls I have had for the wife of the previous owner; every time I say that she moved away over five years ago the caller apologises and says they will take the number off their contact list - but I suspect she was in a lot of debt. You do have to be careful as sometimes an address can be blacklisted and if you want credit you might be refused because of a previous bad debtor. Experian can tell you if all is well for you - It doesn't cost much, just a few pounds.

Debt collectors cannot enter your home or take funds from you without going to court and getting a court order first. Often debt collectors write as if you have to pay or you will be charged even more etc and generally try to put the frighteners on people. If it is not your debt and you ignore them there is nothing they can do and eventually they will shut up. It's not nice though, especially the first time you open such a letter..

The problem is when you inform a firm by phone or post the letter back they think you are the “ guilty” party trying to wriggle out of something. It freaked me out when a letter came from a debt collector which I had opened but had not looked at name. So many times put “moved “ away or something similar on envelope only to get even more of the same.

We started getting letters from DWP for someone we had never heard of with our address except that the postcode was different. At first I returned them “not at this address “,but they kept coming. So I wrote on the front of the next one that we didn’t know this person and that the postcode was wrong for our address. The next one had our postcode too! We opened this one and then rang the number to tell them they had the wrong address for this man only to be told that they didn’t send the letters and couldn’t change the address! It was a different department that sent the letters! They have stopped coming now, but I am hoping that this is not because they have given up on this poor man and closed his claim.

Grandtante, my daughter was advised by CAB that this was what she should do when she was at the receiving end of similar letters for a flatsharer who had done a runner leaving her debts behind.

Please do not open those letters. It is illegal to open post addressed to other people unless they have given you permission to do so.

I too have had to ring firms repeatedly to make them realise that post was being wrongly delivered in the sense that the addressee had never lived at my address.

Perhaps a solicitor's letter might make them update their databases.

Every Christmas I get a card with a small gift inside ( bookmark, hankie, prayer card etc) addressed to a neighbour but using my house number. I always give the card to my neighbours who used to remind his friend of his correct house number - only for the same thing to happen next year! It's quite amusing now and my neighbour always lets me know what the gift is. Neither of us are too bothered although my neighbour is no longer in contact with the sender and does not send them a card!

I did once have debt collectors call at the first house I owned because the previous owner had racked up catalogue debts. I was able to prove to them that the woman no longer lived there and I heard nothing more from the debt collectors. I had been receiving post for this woman but I did not have a forwarding address to returned some letter to the sender and gave other to the estate agent to forward.

I always sent the letters back as I thought it was illegal to open mail addressed to someone else?

Citizens Advice Bureau should be your next port of call.

We had same problem and also son in different house. Still get the odd letter after 16+ years. One from debt collector which I opened and dealt with. It must be quite common. I now destroy the odd unimportant letter as “not known “ gets you nowhere.

But writing the letters will help.

the two phones and the debtor are not linked at all, different people

I have lived at my address for 15 years and still get post for the previous owners. Also get a letter about once a year which comes from Mercedes Benz trying to sell him a new car. This man has never lived at my address, as far as I know.

fizzers by just writing 'not known at this address' and sending it back, you are doing exactly what a lot of debtors do when they receive post, that is why the letters keep arriving.

I think the phone problem arises because the phone number will be linked to your address, so everytime the creditor finds another number attached to your address they follow it up. Many debtors, I regret are determined cheats and go to great lengths to avoid paying up and the creditors have to be equally clever in trying to keep tabs on them.

What you need to do is open the letter and write to the person/company, telling them that you have lived in your house for over 20 years and that no one of the name of this person has ever lived at that address and that you are fed up with being sent these letters. I assume that you have been on the electoral register during your 20 years . You could suggest the company checks the electoral register and credit registers to confirm this.

Write one standard letter and get multiple copies so that all you need to do is put address, name and signature on the letter each time you send it out.

That should sort it out it.

I guess some people who do owe stuff may write ‘not know at this address’ to get them off the trail so if yours is the only address they ve got until they remove it you will keep getting them it’s a shame I d definitely go to CAB

I do realise that phone companies put landline/mobile numbers back into use almost immediately and just my luck to get a mobile number that previously belonged to someone who had a lot of creditors, the landline it seems to be just one company that rings about once a month. As for the debt, well perhaps someone has taken out loans or something online and the company was rather slapdash in their checking.

what galls me is the number of letters I've returned marked not at this address, and the number of times I've asked the phone callers to take the number off their database, do they not listen?

Credit is ok and there's no debts lnked to my address, it's just so annoying

Not credit but DH has had Newcastle (never been there) police ring his mobile 3 times in past 18 mths or so asking to speak to "Jane Smith". DH has had his number for about 5 yrs. So we're guessing she made up a number that happened to be DH's