I have an unlocked iPhone that has GSM and CDMA capabilities. I called my provider and they said roaming would work but I am guessing it would be cheaper to get something over there? London is our first stop, then we are going to Paris, Venice and Rome. Any suggestions on what I should get and if I can get it before I go?
does that work on T Mobile's network?
Yeah I can work on any network, Sprint, AT&T, T-Mobile, Verizon, etc.
I have an Apple 7, unlocked, and bought a SIM card last year for it. I think it costs about 20 pounds for 10 giga's of data and unlimited calling anywhere in Europe. You have your own number which you can text to your people back home in case they have to get hold of you. You have ample data reserves so you never have to worry about wifi. I did the same the year before when we were in Italy and I think that cost somewhere around 15 Euros. I just went to a cellular store, they installed the SIM card and set my phone up. No issues, no problems.
or you can get a T mobile account with T Mobile One which includes hundreds of overseas countries, text and unltd data
When we go to the UK and then onto the continent, we stop at an EE or a 3 store for a UK SIM. They always make sure we are in working order before we leave the store and we have been very happy with coverage.
You might stop at the nearest Carphone Warehouse when you arrive in London, as they offer cell plans with various networks. They'll be able to suggest the most cost effective plan for the countries you're visiting. Be sure you're clear on the method for topping up once you leave the U.K.
When is the trip?
SIM from an EU country work in all EU countries, but what will happen with UK SIM after Brexit is anybody's guess.
They can legally refuse to sell SIMs with 'free' roaming to people who are not resident, but I don't know if anyone has fallen foul of this in practice.