Seems like MTN cant assist with an upgrade request

I used to have a contract with Nashua Mobile (NM). Was due for an upgrade end 2014. NM send me the incorrect cellphone with my upgrade request and I returned the phone the next day (not opened). I then requested the upgrade to be cancelled and wanted new opportunity to upgrade since I have not received a new phone (after 2 year period). Shahida Ferreira (NM) confirmed per e-mail that upgrade of wrong cell was cancelled and I can proceed to upgrade again. In interim NM was taken over by MTN. When (after being referred by 2 other MTN branches up and down) I visited MTN Menlyn (G Floor) I showed Johannes e-mail and he said NM must first update the system with correct termination date. I tried all available no's & e-mails to contact NM without success. I've sent Johannes several e-mails recently which he ignored. 4 days ago I visited Johannes again to ask why he ignored me. He didn't want to take any responsibility to assist and passed the buck. Gave me a new no. to contact NM, which only goes on voice mail (left a message 3 days ago, no one returned my call). Is there no one in MTN that can assist me to do a legitimate upgrade that I'm due for?