If cell phones work off satelites can we use them in space?

It is rather unlikely that the cellular network model will ever be used in space other than fx locally on the moon or on a space station.

The main benefit of a cellular network is that each repeater have a very limited range. That enables us to reuse its frequencies in other repeaters that are distant enough to avoid the two signals (on the same frequency) to be confused. This small size of the cells is also used in network administration because even at light speed there is a delay between phone and repeater, and for parts of the protocols used phones MUST be effectively synchronized with each other (eg: the repeater send an administrative message to all phones in its range "If the signal from your currently assigned repeater is getting bad you can request assignment to this repeater by sending your ID in the slot coming up in .01 seconds". Cellphones respond, but those on the periphery of the cell respond slower because the signal needs more time getting there and back. That forces the slot to be wider to make room for the possible response delays. and the wider the response slots, the less time you have left over to actually transmit signal in.

Distances in space however are BIG, and mostly very empty. It is totally unrealistic to put in orbit a repeater for say every 50 cubic miles of space, and almost none of them would be in use at any given time. Instead I expect we will use directional beams (empty space make it fairly easy to create coherent radio beams that can transmit over huge distances.)

regards JakobA

PS: Iridium was a stopgap solution, created by Motorola, mainly for advertising how hi-tec and ahead of the pack they were. Full cellular coverage require a HUGE investment and before everyone had jumped on the bandwagon and made that investment it was a lot cheaper to put satellites in orbit and use them as repeaters for the rather small nr of phones they were able to handle. Those were not normal cellphones, but about as big as the old walkie talkies and transmissions were mainly directional.