MTN MAKING LIFE DIFFICULT!!!!

can someone please explain to me how my upgrade can be declined??? It's a upgrade! NOT a new account, I have been loyal to MTN for more than 20 years and now they don't want me to upgrade? Yet I received a notification from MTN to inform me that I can upgrade! Apparently the reason for the upgrade being declined is because I'm on debt review? I HAVE NEVER MISSED A PAYMENT!!! By the look of things, when this contract ***) expires I won't be able to renew it? I upgraded one of my contracts last week without issues? So why will MTN be ok with loosing a customer?