Telkom data (on contract)

I have a contract with Telkom, which is suppose to give me 10G of data per month, but i cannot use the data, I always have to buy data on the side. It will tell me I am out of bundle, but when I check the balance, I still have a lot of data - until its the end of the month. When I try to call the call center - calls are ended without ringing. when I finally get hold of the call center - there is nothing they can do to help me. Mean while I know for sure it is not coverage, because Im with people using Telkom and they are fine. I think they want us to pay for the data but not use it.