Telkom line hacked.

My mother is 85. Her Telkom bill is around R500/month, but she was billed R3000 on her statement dated 27 Feb 2022. It is mostly due to a call she definitely DID NOT make for 2 hours to an unknown international number which I think, according to my searches, could be in Djibouti. She knows no one there, nor does anyone who comes into her flat, which is not many people at all. Telkom's lines are obviously insecure and open to hacking, but they refuse to back down from this obvious abuse of her phone line and insist that she pay. This is incredibly unfair and not how a loyal paying customer should be treated.