You have insufficient airtime - on a contract

I cannot make service calls to 200 or 1023, but I can phone anyone else including overseas.<br> When I want to get a directory number using the above, I get an insufficient airtime message.<br> This is only on my ex Nashua mobile contract and not on my four other MTN contracts.<br> I have phoned 808, told that its a contract problem, been transferred to contracts, explained again, passed to technical, explained again, passed back to 808, passed back to contracts etc etc till I kill the call.<br> NOBODY AT MTN KNOWS WHAT IS GOING ON - AT MTN<br> Can someone with a brain please contact me with solution.