Bad customer service

I had an account with MBD,i was paying an amount 385 from Jan to May,and in June was supposed to be called to change the amount from 385 to 158 as that was my remaining balance... Ha ha ha,guess what,no calls were made and surprisingly towards end July,i get i call i owe them 785...i ask hiw,i am told i reversed a debicheck,i asked how and the stupid consultant doesnt know either...i have been getting calls left right and centre fir them to rectify the mistake,nothing....now,i even emailed the supervisor to get assistance,but hey,till today,nothing...they even fail to send a statement to show what is happening in my account...i am willing to settle the 158 but the 785,Never...they failed to do their job now i must suffer....frustrated me. And i still await my paid up letters