free discount on phone and bill - do you think this works?

there's this credit card out that says it give you 5% off all your wireless charges every month, so that means your phone bill and buying the phone, etc. but i was wondering do you think it will work for every provider? i have a sprint phone and a verizon phone so i want to use it only if i can for both. i want to buy the new iphone as soon as it's avail too. if you go to their homepage the review for this card review is on the left hand side of the screen http://www.creditcardforum.com i don't know it says its a business card but u don't need a business to have it... yeah that makes a whole lot of sense haha. has anyone used this or knows if it works for sure?

call the credit card company and ask about the promo
i get 5% cashback on gas and some other stuff with one of my cards