Worst contract mistake

The worst mistake I ever made was getting that small white route from telkom on contract, first I was told by the sales consultant I'll get 15mb of data every month, only for me to get a text later saying I'm only getting 10mb after having agreed that I'll take the router and pay R160 monthly. That bill came with different amounts every months from R240eventually to R1000. I've cancelled the contract and they've debited the amount but every month they debit the same amount and whatever they find in my account they take it but the amount never goes down. I'm so frustrated with this thing that I've even thrown the router out my window and consider changing banks of this. This is the worst experience with a contract lve ever had