Poor service, frustrated customer!!

I have a contract with MTN, I made arrangements to pay the outstanding balance. The next thing I know my account is handed over to debit collectors and I note have to pay an extra 9k apparently for early termination which I never agreed or signed up for.. when I go to their branches , customer service tells me there’s nothing they can do to assist. I am frustrated and stressed. I am willing to settle the outstanding balance just not that early termination nonsense!! I feel ****med !!