Creditors Financial Group

They are acting on behalf of Resurgent Capital Services for a debt of $1618.79 as stated on their letter to me. I agreed to 2 year payment plan in May and allowed them to deduct 67.44 a month from my checking acct. 6 months later I found out 1) they say it was a debt of 1772.26 (I faxed them a copy of their letter and they cannot explain the difference) 2) I have been charged interest fees each month from $3.54 up to $24.00 and each month it varies between those two amounts. Every person I spoke to (including Mr. Ebert Sr. VP) have yet to give me a reason for all this. I mentioned to him about contacting the BBB and he said, don't bother, they wouldn't do anything. I only receive a monthly letter saying they will deduct $67.44 from my account on a certain date - no interest APR info, showing how my principal is applied. Should I contact my bank and tell them not to honor any further deductions from this company? I am willing to pay my debts but not when I have no idea of who I am dealing with and what they are doing with my money.