Vodacom *****S R29 every time I load airtime?????

Every time I buy airtime Vodacom AUTOMATICALLY take off another R29 for a 5GB bundle. I don't press OK or accept or anything else, in fact there is no cancellation button so i just push the back button on my screen to get rid of it but STILL they KEEP *****ING R29 EVERY TIME I buy airtime??? How and WHO give them the right to ***** my money???? and when you eventually get through to speaking to them they just say SORRY I CANT REVERSE IT OR HELP YOU!!!!! I have never in years used more than 500MB of data per month, WHAT must I do with 5GB in one day????? Probably loosing sooo many clients they got to ***** it back to stay in business!!!