MTN router complain/refund for my money

I feel ****med by MTN in SA. I took a router that ddnt hve coverage in my place took it back within a week and cancelled my contract with them. They debted R590 and R78.99 of which thy can't explain what's for thy now refusing to refund my money and when I call they hang up my calls and they are no longer responding my mails. I feel ****med and disappointed cause it's a big company for doing such thng