Not allowing me to move from contract to prepaid

Gooed day,<br> <br> I have numerously called and visited MTN to cancel my contract and move it to prepaid once the 24months are finished.<br> But all the shops i visited told me that i can not notify them more than 20 days before the end period of my contract otherwise mtn will loose the info and my contract will not be cancelled? What do they mean loose? If i want to notify then 24 months before hand I must be allowed to do this. Then I called 808. The first time their excuse was that their systems are offline and they cannot help me. Then the second time they inform me I am only allowed to notify them that my contract needs to be cancelled after the 24 months have passed. Thus meaning that they will charge me for 25 months of my 24 month contract which is ********. How can MTN do this? How can MTN charge me for an extra month after I have tried to cancel my contract?<br> After the 24 months MTN has charged me for my phone and now they want me to pay one month extra for my phone. If they want to charge me for the Extra month they can only charge me for the airtime and data given to me. It is ********* to charge the full amount!