MTN worst service ever

We have been clients off MTN for many years this past year there service went from bad to wors My grandchild is a type 1 diabetic my daugtet had to get a new phone to use her old phone that was on pay as you go for her readings 8 months later her phone is suspended that she pays for every month and recieved calls from a layer stating she owes over R1200 on the pay ad you go she paid that still this phone that her little girl needs is off she keeps on phoning them they root and unhelpfull MTN service is disgusting