Mofire 10 G data deal , Very poor service and disregard

I had a contract on promotion with Vodacom for 10 gig data for 199 pm , the contract was supposed to expire in December last month , Prior to this date I spoke to 11 upgrade consultants telling them to cancel the contract as i dont want it anymore.

All of them advised that they noted this on the system and would do as i asked.

The month after the supposed date , i saw that the data was refilled on the rooter, so i called vodacom and cancelled it again, The lady assured me that it was cancelled.

A month later the data refilled again , so i called vodacom again , told the lady how frustrated it is with such perthetic service and she apologized and advised that the contract was renewed for 24 months on her system, I almost lost it and explained to her that it could not be possible, and that i want the proof where i approved this, After transferring me around for about 30 mins, The line was dropped.

The next day I called again and spoke to another lady , explained the situation to her and she also apologised for the mess , She struggled a while to figure out what was going on with this issue, but at last said that she managed to sort it out.

I was going through my app just now and realised that something wasnt right, As the data was refilled again , but this time i saw something else.

During the whole contract period up to a month before the end date , I was billed just over R 400 and then it showed a deduction of Just of R 250 for the promo, The last month it only showed a deduction of R 100 and for the past two months it didnt show any deduction.

The bill for end of this month now shows just over R 500 how does this happen .

It doesnt help calling vodacom as nothing clearly happens. Ive been a very loyal customer of vodacom for over 10 years , I cant believe they are so careless, How will i get my money back where they decided to take more than they should ?