Unfairly treated

I had a line that needed a cancellation, sent in an email which was not responded to. On the 11th April called in for a cancellation but was rather convinced to take up another plan. The Agent who assisted me failed to disclose the full details on the plan, otherwise I would have declined. Days later all my existing data gone, new data added even before the new month. I've called a numerous times to have the contract reversed and been promised it has been done. Right now I can not use the SIM card cause I want you guys to take what you have processed and give me back my data. Please sort this out am taking this line to another service provider.