MTN Poor Service & Bad After Sales Support

I am a MTN customer and has been for at least more then 10 years. I recently went to the Menlyn store to upgrade my device, for MTN the service was well and kindly done, after struggling at almost 3 different stores to upgrade, then I decided to upgrade at Menlyn, after the upgrade was done I went back to the store because the battery of the phone does not last and for the application I use it for. I am a E Business Field Specialist and need my phone to call Head Office and the sales consultant. by 13:00 the phone is drained and I can't do my job I phoned the call centre just to be ignored and when the people answer the phone they do not assist they just put you on hold. After mailing MTN as well it's been at least a week with no reply.