I received my SANEI N10 today from an eBay supplier and inserted my Tescomobile SIM card in the SIM card slot on the side making sure it was installed correctly. I switched on the tablet and tried to make a phone call. It displayed a dialogue box saying 'Mobile network not available'. I tried a different SIM card and same result. When I go to Settings/Mobile Networks/Network Operators/Search Networks it finds the Tesco 3G network ok and registers on it. Any suggestions on why this is happening? Thanks.