Rude store manager MTN Northgate

my mother has been struggling for weeks to get her brand new phone replaced after it had a major battery failure. She's had to repeatedly uber to MTN Northgate to ask for updates. Today the branch manager was very rude to her and told her that her broken cell phone is not his issue to resolve. This is an unacceptable way to talk to a customer and an old age pensioner. My expectation is that the rude manager calls my mom to apologise and that you immediately replace her phone.