Maybe about 4 or 5 years ago I tried to quit my contract at O2 before it ran out, I had to pay something like 140 quid. I couldn't pay it all at the time and the company was making it very hard to get out. They ended up putting the debt over to link financial. I've had to pay off some student loan stuff off via them before, due to some health reasons meaning I had to quit uni, so I knew what the company was. So because I didnt have 140 I opted to pay them 20 every month when I get paid. This has been going on for years now, I obviously don't owe them that much. I don't have any letters or emails, or anything from link financial now, I don't have any proof of what went on. I have no emails or anything from O2 about the debt. At the time when I realised they were still taking it out I didn't know what I could do. They gave me no customer reference number or anything, I guess I seriously thought the payments would just stop. I've thought about calling the bank and getting them to stop the payment, but I'm worried that they'll send me a letter, and I don't live where I used to. I can't afford to have this, and I highly doubt I'll ever get the money back. I don't know what to do, does anyone here know what I could do?

I was a Full time student in 2019 and have been a PAYE since 2021. They are saying I owe £880 ish which includes late payments. Can they just tell me to pay them from 2019 out of the blue and do I have to?