I sold my old iPhone 11 pro to musicmagpie and got a quote for £360 for it - which they paid. However, the last 2 digits of my account number were in their system the wrong way round so the money got sent to someone else's account.
After spending ages on their online portal trying to speak to someone (and getting cut off twice by their agents), initially they wouldn't do anything because they had sent the money and therefore they "weren't liable".
After a lot of fight by me and posting a 1 star review on Trustpilot, Rebecca S from customer complaints contacted me - I must say, she was fantastic. She communicated with me excellently and passed the details over to the appropriate accounts team to retrieve the payment and repay the correct account. After a few days, she had resolved my problem and the money arrived in my account - thanks so much Rebecca.
Just a shame it was such a battle to get someone to care in the first place, hence 4 stars and not 5.