why can't I get hold of nedbank lawyers???

I have a credit card with Nedbank that has been handed over and I have been paying it on a monthly basis, when I go to Nedbank to find out the balance owing on the account they can not access it, therefore I call the legal department handling the account and they never pic up the calls, I left tons of messages and they have not gotten back to me, I don't know if I should continue paying the account seeing that I don't know the outstanding balance and to my calculations I should not be owing anything, but now I'm left hanging in the dark and very appaled at the service.