suspended line

my line is suspended once again this is an on going problem I have with cell c they insist I have not paid , however I have proof of all my payments , they then request this proof ...I send it through and yet they still suspend it ...in last month I spoke to an agent that confirmed that this error is on there end and my line will be activated yet this month its been suspended. I haven't paid late , missed or short paid cell as long as I have my contract however I still have this problem , this to the end of my contract .this is extremely frustrating even the managers doesn't know what to say when they run out of excuses its real pathetic .I honestly don't know what to anymore .I feel this is really unfair on a customer that pays every single month. Every month I have to lay at least two complaints and speak to more than one manager to have the same thing happen every month.