How do I get a SIM to use in London and Paris?

You won't be able to use the Verison one here. CDMA is not available.
the AT&T iPhone can be used. You just need to pick up a sim here.
Most carriers here now have PAYG nano sims. I'm on Vodaphone which is also good with a bolt on for Europe.

 

The Verizon iPhone 5 is unlocked for GSM use so you should be fine.

And I'd suggest using a pre-paid carrier, I've heard those are all over Europe.

EDIT: You can't use GSM LTE with the VZW iP5, although I doubt you'd get it with a pre-paid carrier anyway.

 

You take the AT&T phone to any phone shop in the UK, and buy a pay-as-you-go sim card with as much money on it as you want. Pay-as-you-go means no surprise charges; when you run out of money it stops working. For example, O2 gives you I think 250 minutes plus 250 MB to be used within a month for £10. If you run out, you pay another £10. In Paris, you probably do the exact same thing.

 

Just find an O2 shop when you get to London and get a pre-paid SIM. Depending on the offer that week, you might need to pay a small amount for the SIM, or you might get it free (which is usually the case).

If all you're using it for is Yelp/Maps/Google Searches/Occasional email, 100 or 200 MB will be more than enough.

Depending on how much the roaming costs, you might be able to use the same SIM in Paris... or just repeat the same process when you get to France.

 

Isn't Vodaphone Verizon's parent company or something?

Anyway, I'd call Verizon and AT&T and ask if they have any partners in Europe. The Verizon i5 is unlocked for GSM, so you can probably get 3G. You probably need to call AT&T and get that phone unlocked. Fair warning that if you're still on contract they may not do it for you.

 

In London just walk into any shop that sells food, magazines, etc and buy a SIM for one pound.

 

Check out this site. I have used them before with good results.

telestial.com

 

I concur that at least in the UK it is straightforward to pick up pay-as-you-go (pre-paid) sims. There are various companies, Vodafone, O2, Orange/T-mobile(EE) are the most obvious.

 

As others have said, get a O2 prepay sim or Vodafone prepay sim.

Check out the rates/charges for using the sim in France here for O2:

http://international.o2.co.uk/internationaltariffs/travelling_abroad

 

Or.... turn the damn phones off. You're on vacation!

 

Because being on vacation does not involve getting in touch with close family members now and then, or because vacation time means one is totally out of touch with what's going on at home, or one may not need to make an emergency call.

 

At least on AT&T you can get international data plans that work in the UK and France that give you some amount of data. don't know cost vs the O2 since I was only going to be in London for 2 days I didn't want the hasle of going to a store etc. But it is an option but I don't know comparable costs.

 

As someone who just returned from Germany and Paris, everyone is correct. Your best bet is to buy a prepaid sim from the local carrier of your choice. One thing I will say is being that you plan on traveling to separate countries in Europe is to actually have them set up the account online so you can add funds as you will need to pay for/buy data and or minutes as your travel. I bought my first prepaid Sim in Germany and figured it would suffice for the time I was there, so I never set up a true revolving prepaid account with t mobile. When i got to France I received a text saying I could use my German t mobile Sim here but at a higher rate and since I never set up my account i could not add funds, and this was my only device to access the internet with so I was SOL and had to buy a french prepaid card for another 15 euro's instead of adding 5-10 to use the service in France. Just FYI