Anyone having problem with Konica Minolta billing system? I was charged twice.

I was charged twice in the billing and they NEVER removed it or gave me credit for the amount. I have been paying more than monthly due and overuse charges as I was advised from the sales rep to avoid service interruption while it was on dispute The current invoice states I owe $374.54 but they send me letter from correction department I owe $2,741.82 while it's still in dispute. It's causing headache and wasting a lot of my time and energy and I just can not understand how the invoice says one thing and correction department says another. They admit it's billing system has errors and working on new billing system but how can this happen? Anyone having same problem?