Bad service TELKOM

Hellopeter, i have an unfixed problem or contract with Telkom. I signed a contract with telkom for Huawei Nova9se in 2022 September. It was a 24 months contract for R300 per month. So after i lost my phone i went back to buy another one and guess what, the supervisor/manager of the Bosman telkom store in pretoria told me that they made a mistake the contract of the phone i lost (nova9se) was supposed to be 36 months and she changed my contract from 24 to 36 months. And i think thats becouse she took advantage of the fact that i lost my contract slip .Guess what I'm not going to pay till they fix that problem. I cant pay R23 000 for a phone that cost R5 500