Poor service

I am now asking for over 4 (four) month for Wonga to send me a Paid up letter. I keep on getting a response that someone will come back to me. The last letter was a month ago that they are looking for the paperwork, due to this is a while ago that their account was paid up to dated. I am trying to clear my name and Wonga keeps on throwing a spanner in the works. I received all my other letters within 1 week from requesting them. Amazing how Wonga can blacklist you but takes them forever to sort out the problem.