Bad Cellphone Contract

I'm having endless problems with my Telkom Cell phone contract I took out a contract in October 2021 I have being overcharged by R40 every month since then..not what I agreed too I have been phoning and going to different Telkom walk in Customer service centre's since November 2021 yes 2021.I got reference numbers but the issue can't seem to be resolved I actually got a msg yesterday from Telkom to say that my contract is due for renewal...What about all the R40 I paid extra the past 21 months