The photon 4g is connected to wimax data. Wimax is Sprint's original 4g network and is only available on certain wimax capable phones. Your iphone does not have wimax capability's due to Sprint decision to stop building out the Wimax network in favor of useing LTE as the preferred 4g data service. Milwaukee and other cities have un-finished wimax network build out's, which are only available in small area's of certain cities.
At some point, Wimax will not be operational for sprint customers whom already own a wimax phone. Also, Sprint no longer sells Wimax phones at thier retail or 3rd party stores (radio shack, Best buy, ect) Amazon and Ebay still sells Wimax phones. but with the rapid deployment of LTE, it would be pointless and waste your money buying one, unless you need one for a broken phone replacement to tide you over until you can use an upgrade for an LTE phone.