Disgusting service provider. Shame on you.

My husband has two contracts woth cell c one for him and one for me, we've been paying our account just to find we are being double billed for a mistake that is on cell c side. A payment wasn't taken by the system hence the double bill. All along I I couldn't understand why we were always overdue amd getting threatening messages to cut our lines. Than a clever me went through one years statements to realize we have actually been over charged because of their mistake. Now no one can tell me how to solve the problem. Collections department is forever busy. I'm don't worh cell c. They keep escalating the problem till who knows where because no one gets back to me.