iphone 4s immediately losing wireless connection

[kimg]

Please HELP! We have 2 iPHone 4Ss and 1 iPhone 3G. 1 4s and 1 3g connect to our home wireless network no problem. the other 4s can connect only when standing directly infront of the router and when you proceed to walk away it drops the signal (within 15 - 20 feet of the router). Thought it was the router, linksys had me buy a new router. happens with the new router as well. now they are telling me it is a setting on the phone. I have compared all settings and they are all the same. Any suggestions would be GREATLY appreciated. It's my daughters phone and the overages on the data plan are starting to add up.