MTN not helping PrePaid Customer!!! Worst service ever!!!

My Dad is a PrePaid MTN subscriber since the 073 numbers started, and since September 2023, he is unable make phone calls, but can receive calls. he spoke to the MTN shops in Brits for assistance, and they do not get back to him. They tell him they will follow up on the issue, and still no action. He uses the number to run his business, and needs a second phone now to receive calls, and the other to make calls. This is such a discomfort and needs this issue to be resolved as soon as possible.