Telkom blocked non oweing contract phone

Hi guys my name is John and I can't begin to express my frustration with Telkom, my sister took a phone on contract in her name to help me out, and ever since I have never had issues with using Telkom as a mobile provider, as my 2 year contract is coming to an end this December 2021 Telkom decides to hard lock my phone in other words blocking it and rendering it completely useless, my contracted phone has no arrears, we owe them nothing but I have to struggle with a blocked phone for almost 5 -6 months now but every month paying my contract of almost R500 a month without fail, is this fair?? I went to the store no help, I called their customer care spoke to them and till now I'm still waiting for their response, Telkom is known for their professional service but after this pathetic and discusting service I will no longer be there customer or take any contracts with them, why block my phone?? I don't understand.