SHOCKING! I would definitely complain Mymm. I absolutely abhor bad customer service! In my younger days I just ignored it but one advantage of becoming a GOW is that I am not afraid to complain now.
Like someone else said, put it in writing! I always write detailed but polite letters. Most, although not all, are responded to very quickly and hopefully sorted internally. TBH I just absolutely hate being treated badly.
In one very large store, I saw sachets of face packs (you know the ones that you smear on and then leave for 5 minutes and you look 30 years younger When it got to the conveyor belt, the yawning assistant threw it back at me! "Its got no bar code on, I can't scan it" So I said its 99p...she said "no good, I need a bar code". So I said well can't you get a bar code and she cheekily said "Nope, all of them are the same". She then held her hand out for payment of my other goods.
I didn't lose my rag - I simply left her standing there (with over £70 worth of unpaid groceries on the belt) saying "I will find one". I took my time getting back to the display stand I had plucked it from THEN picked up the WHOLE display stand and struggled down the aisle with facepacks flying everywhere, and plonked it down on the conveyor belt "Ok pick one", I said" HAHAHA you should have seen her face, it was a picture but .....she managed to get my 99p facepack through no bother.
Then I went to customer services and complained and followed up with a letter telling them there was no use spending millions proclaiming every little helps with staff like that!
I got a massive apology plus a voucher (although the voucher was not what I was looking for) So yes complain! The bit about her trying to fob him off with the tester is dreadful and unlawful surely? Good luck and what a fabulous grandson you have.