Right. Before we start, I am not feckless with cash, nor do I have out of control spending habits. This is a matter of principal 
Five years ago, I opened a credit account with Oli (fashion website). Long story short, they were shit. I bought £200 worth of stuff from them but it never turned up on time (ordered loads of holiday stuff from there as they went up to an 18 and I couldn't find nice holiday clothes anywhere when I was lugging my baby weight about) and then they sent wrong sizes etc etc. I rang them (this was in 2006, BTW) and told them they were not good enough and that I wanted to settle my account. I sent a cheque for the balance.
About a month later, I got a letter saying thanks for your payment but you owe us £35 as your cheque did not clear before the payment due date. Not my problem, said I. I sent it well in advance, I didn't know it would be sat n your office waiting to be cashed for nigh on two weeks
Told them to whistle about seventy trillion times. Next thing, they add another £35 for "administration charges" I laugh at them again and tell them I'm not interested.
THEN, they pass it on to a debt collection company. They rang me at home, I explained calmly what happened and they said no sorry you have to pay and will incur more charges if you do not. I refuse still. Basically, it crept up to £140 with a tenner being added each time they sent me a letter. In the end, I told one of their phone people that they were wasting their time and he told me explicitly that he would write the debt off. Definitely said that, in 2006.
So, was most surprised to get a phonecall today from a debt collection person asking for this £140. I lost my rag a bit after explaining it all again. I don't even know how they got my number as I moved over twelve months ago. It's "only" £140 but it's the principal. They're not bullying me into paying it. I told the woman as much and she said "you WILL be pursued for the amount" Vague threats don't wash with me. Next time they phone shall I tell them to eat their own shit? I'm not being harrassed in my home for a debt run up out of what essentially the laziness of the company I had the account with 
Sorry for long post.