Can I bring an unlocked Google Pixel 6 to an existing plan to replace my current device?

As long as it is a compatible model, you can bring any phone to AT&T.

Before you buy...

List of compatible phones

Or imei check 

https://www.att.com/buy/byod/identify?devicetype=phone

If you already have a phone and sim, you don't need AT&T involved at all you just move the SIM card from the other phone. 

@formerlyknownas Thank you for your response. So by simply migrating my existing SIM card (I believe my four-year-old Samsung and the new Pixel both use nano-size SIMs), it should just work? Number transfer and all? There isn't some sort of validation that occurs on AT&T's side that says "Hey, this isn't the phone we have on record!"?

So by simply migrating my existing SIM card (I believe my four-year-old Samsung and the new Pixel both use nano-size SIMs), it should just work? Number transfer and all?

Yes and yes.

There isn't some sort of validation that occurs on AT&T's side that says "Hey, this isn't the phone we have on record!"?

Your account should update with the imei of the new phone automatically. If for some reason it doesn’t, then you may need to call to update or update online.

@sandblaster Excellent, thank you for your assistance!

Hello muad_dweeb, we're here to help you with replacing your device with Google Pixle 6.

As our Ace stated, please make sure the unlocked device is compatible with our new network. If you have a 5G device, you also need a 5G SIM card for the device to work on the 5G network.

Here's how to swap active SIM cards between devices:

If you have a 5G device, you also need a 5G SIM card for the device to work on the 5G network.

Ah, well this changes things a bit. The Galaxy S10e did not have 5G compatibility so I probably need a new SIM card.

What does the transfer procedure look like if I have a new phone AND a new SIM card? I imagine this will now require some coordination with AT&T.

The Galaxy S10e did not have 5G compatibility so I probably need a new SIM card

Not necessarily. I upgraded from an iPhone SE (first generation and not 5G) to an iPhone 12 moving a 4 year old SIM card. The iPhone 12 gets 5G just fine with that SIM card.

Go ahead and move the SIM card from your old phone. If you are in a 5G area but still don’t get 5G after you are sure your account shows the new phone, then go to an ATT store for a replacement SIM card. Give it a day or two, it can take that long for the 5G update to your line to occur.

@sandblaster Okay, that sounds promising.

It sounds like the worst-case scenario if I migrate my existing SIM is that the new phone only gets 4G, but should still work overall. Then I should be able to upgrade the SIM afterward if I feel it is necessary.

Hello muad_dweeb, that is a good question about switching devices.

You can activate the new device and SIM online. If you bought a new Android phone or a new SIM card, make sure the SIM card is inserted in the phone. 

Let us know if this answer your question.

Thank you for visiting AT&T Community forums.

Carlton, AT&T Community Specialist 

Yeah I bought a pixel 6A and moved my SIM card for Verizon and have no trouble getting 5G. I don't believe AT&T will give you any trouble.