Wrongfully billed

I bought an IPhone 7plus at Telkom on 1 gig free me. The next thing my bill is R500 over, when 8 asked they tell me that my profile was not capped. How? When I bought the handset, I was told I could not buy the handset without a sim. So I bought the 1 gig free me sim. How the billing is over R1500. I bought a 1 gig free me but they say it’s uncapped but no one really explained to me that the 1 gig free me package was uncapped. This is day light ******* because they should have told me on this uncapped because according to my knowledge, the 1 gig free me data is for what’s up message and other messages and that is all.