Struggling with feedback from Debt Rescue

I have been a client with Debt Rescue for a couple of years now and at first was very impressed with their service. However I have experiencing problems with them starting this year. One of my creditors claimed that they were underpaid and that my account is thus in arrears. I have been calling and sending emails but the problems continues. I have requested that I be called from someone at Debt rescue to assist but no one gets back. The only thing they did was send documents to the creditor but the creditor insists that they were underpaid. When I call my call either gets cut when being transferred by one department to the other or I get promised that they will sort it out. It is now 3 months later and the issue is still unresolved.