HomEq Servicing Cannot verify where they have applied payments/overpayments North Highlands California

Has anyone else had a situation where they have either overpayed their payment and asked for the additional money to be applied to their principle or been told to pay a certain amount and then been told that HomeQ has no idea where the additional funds were applied?
We fell behind on payments, but were told the amount needed to make the past due up, including late fees, advances, etc. I paid said amount and now doing the math, I show that over a little over $1650.00 cannot be accounted for. Homeq has also admitted to not knowing exactly where the funds were applied and cannot explain why the online mortgage service is showing that EXACT amount being applied to thenext due payment. My account statement online shows that my next payment is $1650.00 less, due to this overage, but customer service is telling me that it is not showing this way in their computers. I have printed out my statement showing this credit, but do not know hwich amount to pay. They have a history of not applying additional funds and then writing them off as "advance fees" or "misc. fees". I cannot afford to let them do this again, but aslo cannot afford more unexplainable late or misc.charges. Any advice?

Mmatthews
indianapolis, Indiana
U.S.A.