INCORRECT CONTRACT CANCELLED

I made a to the call centre @ night on the 28-02-2015 so that a contract that i finished on the 13-02-2014.I asked the consultant to cancel my exp[ired contracted then she told me she will put a note on the system for the cancellation department to cancel my contract that expired and on the 14-03-2015 when i had to receive airtime for my contract that was suppose to be active i had to find out it is was changed to prepaid.To conclude I have 3 contracts with MTN and as a customer of Mtn i would like to know why would I want to deactivate a contract that i have for less then a year.And keep a contract that expired active it just doesn't make sense.VERY ANGRY!!!