I want to change my T-Mobile phone to Vodafone. I'm going to buy a new Vodafone Sim Card from the Vodafone Online Store but I would like to know if the Vodafone Sim Card will work on a phone that came with T-Mobile.
You need to work out if your phone is locked, the only real way to do this is to try a sim from another network. you must kow some one who'll let you try.
What phone is it? some are easier to unlock than others.