Telkom cellphone contract "Phone not working"

I have samsung s21 plus on contract with Telkom. I have had issues with the phone switching off and on automatically, freezing, deleting wats app messages and apps stop working. I have been to telkom pavillion on numerous occassions they said update software everytime. They then booked it in for 1 month i had no phone and still it comes back same problem. I go to the again and they say send in for software again. Im fedup and tired of it. The phone cant be used for long, i asked for a new device or cancel contract or upgrade and pay the difference. They all say they cant do it. Telkom at pavillion "Justin", he said he will mail all the managers supervisors etc.....and again they said they will contact me

Im still waiting im paying gir a phone that i cant use Please help me get this resolved with some assistance urgently