I've got an old Samsung A400 cell phone that I recently cancelled service on and have agreed to give it to someone else. I'm a little concerned though. If I dial a number, I get a message that says 'Welcome to so-and-so roaming network; Charges will be such-and-such. Enter the number you wish to dial blah blah' If I look at the settings on the phone, my phone number still shows up. Is there something else I should do before giving it to someone else to use with their own plan? I don't want to get a big bill in the mail a month down the road. Do I have to take it to a Sprint store to get it deactivated?