Poor service

I have a top up contract which costs me R224 per month with MTN for almost 6 years now and in the middle of October 2015, I added a special of 2 tablets for R198 to my current contract through Summer Mobile, a service provider of MTN . At the end of November I was billed for R1200 as I exceeded my bill limit which I wasn't even aware I had. After querying this with Summer Mobile, I was reimbursed the full amount, as the agent never disclosed that part of the contract. They advised me to Change the limit which I did after receiving 2 calls from MTN. At the end of December I was billed for R1924. I queried this with Candice Beukes, the customer service Manager at Summer Mobile who has been trying to resolve this problem ever since with no success. I reversed the amounts debited from my account and at the end of January my account was suspended. I haven't had a single response from MTN over the past 2 months and have since changed my Sim Card and I'm now using Cell C.