Close Premium Finance

I recently looked for cheap contents insurance on moneysupermarket.com and found one that was £15 a month. I barely even remember the name of the company, but looking at my bank statements it appears to be Resell Insurance. That sounded fine so I signed up, and it was fairly straight forward.

Skip forward 6-7 months and I didn't notice that my joint account was empty when they tried to take a direct debit. Two days later I got a nasty letter from 'Close Premium Finance' - a company I've never ever heard of - saying that because I'd missed a payment I owe them £30, but I shouldn't worry because they will take that with the other £15 and so £45 would be going out of my account in the next few days.

I immediately cancelled the direct debit and found another insurance company.

I drafted a letter to them saying that I won't be paying the charge and that I would like to cancel my insurance, but haven't got round to sending it yet. Today they sent me another letter with an attached 'default notice', claiming that I need to pay them within 10 days.

What do I do?