Declined upgrade

Can someone from credit management get in touch with me urgently with regard to my upgrade that was declined due to the new system and something on my name. Ive been a customer for a few years with an excellent payment history which should count for something and ive upgraded before now i cannot upgrade. Did phone mtn but they do not want to put me through and say they will get someone to call me. I need to speak to do in that dept asap. Ref ***