Poor service

I have a contract with Vodacom. My account keeps on being added R500+ amounts I don’t know about, they said my contract was in arrears for 3 months that’s why they added the first R500 which is not true. Now when I call again for the second one they tell me it’s a reduction amount of the contract I am paying. I complained the first time they stopped my line for a day and then they added another one. I’m not sure why is this happening. Also I just paid end of March and they took all the data I had and airtime.