Bad Customer Service

My Mum took a contracts with MTN telephonically. The 1 specific contract she stated to the call centre agent that she wanted to use a current number for. The agent advised her once she receives the device she must go to the store. She has been to different stores and no one is able to assist her. She has even being trying to contact the contact centre to port the pre-paid number to the new device but to no avail. Guess what she has already being billed for a device that cannot be used as there seems to no one that can assist with this issue urgently.