Double Debit

I am so dissapointed with MTN and I don't know what to do anymore. Few months ago I was charged a cell phone insurence premium when I did not even have an insurence with them, they had used my wifi router simcard number which is even in a router not a cell phone. The matter was resolved. They have recently started debiting R400 and some Rands every month again instead of debiting only R199. 90 per month for my wifi router. I am tired of following up, what hurts the most is that no one is helping, everyone keeps transferring me, even the store where I took the router contract is not helpful. It's just so sad that when one takes up a contract, ones you're done you are no longer treated well.