Got my fingers burnt

I had a contract with Telkom Mobile for over 4 years for a laptop and a data line. I managed to complete payment of the laptop and kept the contract since I was receiving 2G of data for only R100/month. In December 2020, I received a bill of R365, which escalated to R1 765 as of 06.01.2021. After calling customer care, I am told that these were internet subscriptions. So Telkom has no way of blocking third party subscriptions? and why are they only popping up now, after using the line for 4 years? Long story short, I cancelled this contract and will never have a contract with Telkom again!!!!