Mobile Phone Coverage

Would still have to confirm with someone, but there seems to the possibility of cell phone use at the peak. Vodacom Tanzania uses GSM on both 900 & 1800 Mhz frequency but I'm not sure if they allow roaming. But that means we could probably rent/buy a cheap phone rather than using a satellite phone (or none at all). My trusty Sony Ericsson T616 can use 1800 but not 900 band.