Cell C billing is incorrect

I got an email stating I need to pay R907.01 where I already paid R939. 40 last month and where is my free 1 month promised to me. I have not received any feedback on this..

My black box is still not working.

I AM FED UP WITH CELL C

If you do not fix my account before Tuesday 9th of April, I will be contacting my lawyer to handle this case further.