Unauthorized deduction on my number ***

My experience with telkom is now turning into a nightmare, I now think of ditching my number and getting a new number, they keep taking my airtime, purchased R50 airtime to buy data with now again the system tells I don't have enough meanwhile it gives me a balance of R51 free airtime where's my R20 gone to, why why the worse part I can talk to them directly, they use self service which is limited. To me this is a daylight *******. HELP ! WHERE CAN I GET HOLD OF THEM, Anyone please