Renewing contracts without customer permission - cannot get any feedback

I have a 5gig router which expired last year. The sales team tried to sell me a better deal, able to give me 30gigs for the same price as the 5gig router. I explicitly said that I do not want a new contract, that the 5 gig contract was ending. They said they would just change the data on the contract and I advised them I have fibre and dont need two routers, let alone 1. I was promised that I would only be billed for the one. I checked my statement to find out they have renewed the 5 gig contract for another two years and now also billing me for the 30gig router. I have called them multiple times trying to resolve this and they are absolutely useless with their service as everyone promises to come back to you and no one ever does and you just have to keep paying. They do not have the customers best interest at heart and dont bother to listen to your complaints or come back with any feedback. My cell phone contracts are up for renewal and I will not upgrade with them again and would rather go to MTN