A:AnswerWhen purchasing the phone it will come with a Verizon sim card. For example, I switched from Sprint to Verizon when I got the phone, so they transferred my number and everything was fine because the phone already has a Verizon sim card. If you are looking to use this phone and not with Verizon, you would have to get an unlocked phone which is more expensive.
A:AnswerYes you can't get a phone without a carrier activated service. You can buy the phone out right full price but not worth doing that just for wireless headphones. If that was what you meant by "keeping it wireless".
A:AnswerI believe so, but you have to activate with Verizon first. Once activated, you can take your Verizon sim out and put any other sim card. It should work. I did it within same hour of getting the phone ( I switched from Verizon to AT&T)
A:AnswerIt should, yes. The Pixel 3 unlocks after it's purchased. I got mine on Verizon and about an hour after setup I got a message that the device was now unlocked. I don't plan on leaving VZW but it's good to know!
A:AnswerOnce you purchase the phone, you would be able to get it unlocked by calling Verizon for the unlock code. Then you would be able to use it with AT&T. Of course, you will need an AT&T sim card.