Cell C's inadequacy

Cell C keeps sending me sms's that they going to suspend my service and that it's going to reflect on my name and then they do suspend the service. When I call they can't find the problem (even send them prove of payment) and activate the service immediately and two days later the problem repeats itself. This morning they suspended the line while we were on the phone with them. I've got 5 lines with them with 4 other people using these lines but every time there is a problem they insist to speak to me only for security reasons but this means I'm more on the phone with Cell C than my wife. Unfortunately it is costing me not only time but money to sort their problem and I would like to know who I can invoice for my time. I regret to say that the only time I get almost the same standard of service as a Vodacom for example is when they trying to sell a contract to me. Then they can actually talk to a third party and arrange anything to close the deal but that is where the service stops. Further when you want to get the operators name that tells you not to get irritated with her she puts the phone down in your ear?