Number deactivated by MTN

I have a MTN prepaid number that I use occasionally. I switched on this sim over the weekend as I needed to use it. It shows \sim not provisioned\" so I call the call centre for assistance. They tell me that the number has been de-activated on 29 January 2016, due to it not being used for a while. This is not the case as I make it a duty to call this number on a regular basis in order to keep it active. I paid alot of money for this number, just to be told that iv now lost the number. Please sort out urgently!"