How much does the iphone 4S cost at walmart for 2 year contract?

Ok i have phone for virgin mobile and it only has prepaid minutes i also want to get an iphone 4S on my next payday. So i also want to know how much it cost to get unlimited of minutes also?

For a 2 year contract it should be $99 but it may be different for virgin mobile but its $99 for at&t Verizon Sprint etc so I don't see why it would be different for them