Given the run- around for a paid up letter

I recently had an account with Edgars which was handed over to VVM attorneys. On the 2nd January 2018, I settled the account and was given assurance that the account is fully paid. I have been waiting more than a month for a paid up letter, each time I call Edgars they say that VVM should zero balance the account, however when I contact VVM I'm being told that the account is no-longer with them but handed over to Edgars again. Its been more than a month and I haven't received my paid up letter, Edgars says that VVM will make contact with me. I really don't know what to do as the default is ruining my credit score and I need to buy a car urgently.

Edgars least you can do is keep to your promises of 21 days and remove the default.