Being over charged for an iPad how to cancel!

I was offered a deal where I would pay the same amount for internet (about 60$) and I would be given a free iPad. They explained it would be 30$ for internet and 30$ for iPad, I would be paying 60$ for internet regardless so I agreed. Its been over 6 months now and every billing cycle I'm being charged 60$ for my regular internet, plus 29$ for the iPad, they are charging two different cards, I did not agree to pay 90$ every month, the agreement was 60$ not 90$. I want to cancel this iPad and have my money rightfully returned.