Misselling

I upgraded online in February and the phone I chose showed only R550.00 monthly, to my surprise end of March I was overcharged and on calling customer care I'm being told of an extra R149.00 for airtime which was not mentioned on my application. I never bugdeted for such an amount and need urgent assistance in this regard. Even if it means I do not get the airtime monthly that will suit me fine because I feel this is ****************. I've been using Vodacom for a very long time and never on my package have I ever paid extra for airtime being awarded to me. I really do not mind paying for the handset only but am not prepared to pay this R149.00 extra