Cancelled mobile contract with Carphone Warehouse in January. Cancelled DD with bank. CW attempted to get DD. Same in Jan then Feb then March. Then I got debt collectors letters so wrote to cancel again. Still trying to collect money from DD. I've now paid debt collectors £58 to complete closure BUT CW still say account live and that I hadn't sent the closure letter by registered mail!!!!! Thety've now added another £20 to account. What can I do?