Payment billing concerns

I'm trying to make an early payment and it's saying one or more details I entered are incorrect but it's highlighting my security code. I'm holding my card in my hand and checked and quadruple checked and all the details are correct and it still won't allow me to make the payment. Also when I signed up with Xfinity I was promised 4 free phones , that they were offering a no activation fee that day and that I would receive 4 $50 prepaid MasterCards for signing up with Xfinity and bringing my phone number to your company. I payed $40 on the first day and my first bill is due Feb 24th for the billing cycle of January 3rd to Feb 3rd and the charge is $193 and some change. My bill is supposed to be $80 per month so what are these extra charges for? Where are the promised prepaid cards and why isn't it excepting my method of payment. It's basically saying it's the wrong security code but it is not the wrong security code. Please help. Thank you.