6mnths of stress

I've complained about CellC for months and honestly NO change cellc sends me a statement that I owe nothing and then send me one saying I owe R878 and deduct R1600...I dont even want to talk to their rude agents and managers..I've opened an investigation since October and when I called to check the guy who was doing my thing closed the tickets...EVERY MONTH I fight with cellc...at this point I'm seeing what legal action I can take cos this isn't ok anymore...