Unable to get my contract no to prepaid since canc

Notified MTN in January that I was going to cancel my contract once it ended in April. Since cancellation on 17 April the number still has not been changed to prepaid after multiple emails to the customer care department. The only rsponse I get back almost every other day is that the call has been escalated. What exactly is done when the call is escalated multiple times? is this just a general response sent out by MTN? I already have another contract running parallel to this that cannot be used thanks to MTN not changing this Number to prepaid which means that I cant port the MTN number to another network! So tired of issues with MTN!