Unauthorized Contract upgrade for a pensioner

I don't understand how Vodacom works. My mom's contract was supposed to end at the end of March 2025, but out of the blue, it was upgraded to 2027. How is that so because she did not subscribe to this or agree to it? She went and complained, and they said it was not reversible. What kind of products are you selling to our parents, and she's a pensioner?