I can't seem to get cell reception outside the Invercargill boundary- attempted to send txt at East Rd, kennington, Dacre, Edendale all said sending failed. At Gore could not send a txt either & came back with message saying 'not on registered network'. I have recently changed from Spark to Vodafone & not experienced this before. Full reception showing on screen but not able to send/receive any txts or phone calls, tried restarting phone but exact same message came up again. How can I get reception outside of Invercargill?