Abuse of power

I took a contract with VODACOM for 199 per month In 2018 ,I paid only 199 for the 1st month all of a sudden come the 2nd month I am sent an email stating that my payment will be increased to R204 per month I did not default on any of my payment when I asked why I was told that it is like that and if a have a problem I should do what ever I see fit. I continued paying even though I felt abused . Now it is almost time for my contract to come to an end.i am expected to pay 405 cos I have defaulted so they say . . Of which I did not I just used a different method of payment. And my benefits are confescated without a valid explanation. I have tried engaging with VODACOM of which I cannot get someone to assist. I feel like I am being abused because I am a black person and I allowed myself to be abused .