Rotating sim cards in one phone

Yes, I have done this on past trips. Just take a paper clip to eject the SIM tray. My unused SIM lives in a small plastic box in my jewellery bag. I only swap them out so I can use my usual SIM to check text messages. If you just want to browse the internet using your hotel wifi you don't need to swap your SIMs.

The only downside is that you need to be really, really careful not to lose your SIM card while changing it.

Sorry, but I don’t understand why you feel the need to switch SIMs. When traveling, I just keep the locally purchased SIM in my until I return home. I usually switch them out on my return flight.

I do the same as poster above, swap them on flight home.

@Philip, I need my US phone number mainly for 2-factor authentication, as there are a few accounts I'll need to access while abroad. (Including email, which I'd planned on checking daily.)

But maybe it's time to bite the bullet and switch to an authenticator app...

I will jump in to say I was very happy with the giffgaff sim card we used in England last year. They will send you the card ahead of time to your US address, no charge. Download their app and set up an account. Follow the instructions sent with the sim to activate the card and purchase a plan. It was incredibly cheap. I think £10 for 20GB data and unlimited calls/text in the UK. The plan was good for 30 days, no rollover. You can also purchase smaller or larger increments of data.
https://www.giffgaff.com/

@Katheryne Thanks! I've seen Giffgaff recommended a lot on this board so I went ahead and ordered a sim from them.

Mary, consider signing up for Google Voice. This gives you a second (free) US phone number for texting and calling, via the Google Voice app. You may be able to switch your 2FA to your Google number. I've been using Google Voice as my regular phone service (or rather, WITH my regular phone service - still have to have a mobile plan), and I use my Google number for 2FA all the time. It MOSTLY works fine - but once in a while some institution doesn't like a VOIP number like Google Voice so they'll either reject the number or your texts just never arrive. Facebook is the one I use that rejects my Google number outright (so I don't use 2FA with Facebook).

The other nice thing about Google Voice is that you can make free calls to US phone numbers, even to landlines, while on WiFi or with mobile data. You can certainly do this using your Metro SIM card with WiFi calling of course - but that's a bit of a pain right?

Generally you do not need to switch SIM cards in order to use Wi-Fi on your device. You actually don’t even need a SIM card in your phone to use Wi-Fi. On the other hand, if you are trying to access services from your carrier or data stored on a particular SIM then yes that card needs to be accessible.

raymonelee, she wants to use WiFi calling to call/text with her US phone number, so for that she will need her Metro SIM card in her phone.

Chiming in to comment that you need to check that multi factor authentication works over wifi with your current SIM, otherwise your plan won't work (I'm not a tech person, but I am not certain it will if your phone does not connect to a cellular network). For your scenario, it may be simpler to set up an authenticator so you don't have to worry about it.

You don't say what type of phone you have, but a possible alternative is to set up a Google Fi account before you leave - you can order a physical SIM. You'll have a known US number and can give that to friends/family that want to text, as well as setting up the MFA with your email and banks using that number. Then you don't need a UK SIM at all.

Most of the time it works, but sometimes the phone needs to have some settings changed so the new SIM card will work. Just be aware of that. The hotel will probably have wifi, and as said already, you don't need any SIM for that to work.

CL:

Chiming in to comment that you need to check that multi factor authentication works over wifi with your current SIM, otherwise your plan won't work (I'm not a tech person, but I am not certain it will if your phone does not connect to a cellular network).

There's no reason it wouldn't work if she has WiFi Calling set up. The entity using two factor authentication does not have any idea whether you are using WiFi or mobile data - they text you a code, that's it. If your phone is able to receive a text message - because it has cellular service or because WiFI Calling has been set up and working - then you will receive the text with the code. She has presumably already used and tested the WiFi Calling feature on her phone at home and knows that it will work that way. if it works at home, it will work in the UK as long as she has WiFi...and she has her Metro SIM in her phone.