Vodacom is a ****... don't do contract

I have a contract with Vodacom for only 160 data of which it is 150 data and 10 rand cli, it was ok up until I do the airtym advances, of which they ended up adding on my bil, without informing me, I let the deduct the first time, then the 2nd time I reverse the debit order, and call them as the amount was over 800, that's where they told me about my advanced airtime, I then negotiate with them to take all the money in march of which they did, then the consultant told me after this payment I won't owe them any advance anymore as the previous month in February after a call I requested them to block my airtime advances, of which the did, to my surprise in April after not buying any airtime for the whole month to just c how it will go, the bill was 170, not 160 anymore, then I became relieved and started buying airtym only in may, boom! There comes another bill, of which I don't know of since my advanced airtime is blocked even now, I reversed the money again and call again they told me it's for advances but on my account she could see the advances are. Blocked , the consultant couldn't explain why the amount hence the blocked advances since February.... please help as I called them several times and no help, the bill is going up every month ,my contract ends in August this year