Not something I didn’t order, but something I did order for free. Years ago, in the early years of on line shopping, I was perusing the website of a well known brand of cashmere clothing, and noticed that there was a glorious cardigan showing a price of £0.00. I was genuinely curious so I ordered it in four different colours, just to see what would happen. At check out it calculated that I needed to pay £4.95 delivery.
They arrived, and I wore them all. Several months later the company contacted me to ask for them back. I checked with Which? legal advice line, who said that (a) the postage payment constituted a transaction from me, which counted in law (don’t ask me how) so I didn’t have to send them back, and (b) they needed to send me a means by which they could be returned e.g. prepaid envelopes. I pointed out to the company they were now used cardigans, but I would send them back if they arranged to collect / prepaid envelopes. They never did, so years on, I’m wearing one of them whilst I type