No service from FNB

I have a revolving loan with FNB and have already paid back more than 15 % of the loan, yet none of that credit has become available again. I have phone my private banker numerous times, trying to get an answer as to when the credit will be made available and he is always "not available", then I am being transferred to the switchboard and then from there to a bunch of endless menus to choose from just to get an machine answer telling me that my request cannot be supported, I even spoke with a lady at the loan department telling me she doesn't know what to do, I mean really!!!!