Hi there, my GF is over halfway through an 18 month 3 (Three) Mix and Match deal (M&M 300 I think). I want to give her my old iPhone 3GS, but really she could do with a data tariff adding to her contract to get the best use out of it. What is the best/cheapest way to get this? Any ideas? Obviously the cheaper the better. Any way to change the tariff over halfway through the contract term? cheers!!!