False Marketing

I bought 100min voice minutes today from vodacom app and selected an option for the amount to be added to my monthly bill. The amount was at 40% discount and immediately they adjusted my bill with the amount changed. Now they only added 32 min of the 100min, apparently when they add the amount to the bill they only give you pro-rata but the bill is in full and not pro-rata. Am I crazy to buy 100min when I needed less minutes? If I needed less minutes I would have bought less minutes. Vodacom your misleading people with your promotions staff and false advertising. My bill was adjusted in with full amount and I need my full minutes. The inconvenience when my phone cut off when I was on a call.