NONSENSE service

I got a sim card contract from Telkom through Mondo and the sim doesn't work, it's been over a month now and it still doesn't work. This morning I received a statement saying I owe R175 with a sim that has never worked and my contract was for R99, I don't understand why I am paying such ridiculous amount for a service that was not provided to me, why are companies taking advantage of people and ripping them off with no consequences? If I was to reverse the DO I would be unfairly blacklisted, what kind of nonsense is this?

I want all my money back and they can keep their poor service to themselves. I have tried multiple times to get an agent from Mondo to call me and nothing to this day, NO this is NONSENSE!!