This is a question that shows up in many threads. It might be a good idea to have one thread where posters can share recent discoveries and experiences in buying service in Europe.
To get it started, here is an offer for data in Europe at 5 Euros for 5 Gig. It sets the tone for the competitive nature in Europe. Buying a local SIM card opens the door to Skype, Viber, Facebook, and similar VOIP. Certain packages might be restricted to local residents, but there should be plenty of choices.
If you have T-mobile, they have free global roaming to 120 countries. Also, they have Wi-Fi Calling.
Wi-Fi Calling allows you to make and receive calls; access unlimited high-speed data; and send and receive messages over a wireless internet connection. If there is a wifi connection anywhere on earth, your phone works the same as if you were on T-mobile’s network in the US. Works great.
^ Regarding T-MOBILE, there is a caveat. For instance in Mexico, the connection is at the lowest bandwidth and is barely useful. Check the authorized connections “speed” in the target country. My family tried the service with MIFI and direct connection, and the results were not worth the efforts. A local SIM worked much better.
This said, the service could be a nice complement and much better option than the ATT or Verizon options abroad.
Piggybacking on free WIFI is different from getting your own data source.
This is quite timely for me as my daughter will be studying in Denmark. We’ve decided to go with unlocking her phone and purchasing a SIM card in Denmark. However, we have no idea which carrier we should use. Anyone have a specific carrier recommendation for Denmark?
ClaremontMom, she will figure it out when she gets there. I have a “nomadic” kid, and that’s what she always does: asks the locals, the other exchangers/interns and buys her SIM cards locally.
That’s the current plan, but it would be nice if she had an idea ahead of time (worth a try asking here!). I’d like her to have a phone as soon as possible after she lands. Once she’s there she’s without a phone (except for Wi-Fi) until she gets a sim card. I’d rather she not spend a lot of time shopping around and “asking locals”.
Here is a list of the MAIN providers.
https://en.wikipedia.org/wiki/List_of_mobile_network_operators_of_Europe#Denmark
Please note that there are a number of smaller companies that resell and package the services of the main operators. For instance, most large retailers such as Aldi or Dial are offering discounted prepaid SIMs that operate on one of the larger network. Usually, the main operators have a faster service and better coverage than the discounters.
For a longer stay, one can buy different services. For instance, in Belgium, I bought a SIM for the iPhone from Proximus because the coverage was better and the connection faster. On the other hand, I loaded a SIM from Viking (see above) in my iPad and router as I was using that one from the apartment. The combination of both was 30 Euros and I had 5 GIG of data. Since then the prices have come down. The only downfall was that roaming was expensive. Hence the need to buy different SIM card in different countries.
All in all, it’s a lot cheaper than in the US. The direct cellular connections were also 10-12 times faster than at any “free” wifi spots.
Thanks for the link and info xiggi. If anyone has personal experience with any of the carriers (either good or bad) I’d love to hear it. Otherwise, we’ll just take our chances (I guess that’s the good thing about no contracts, she can always change if a carrier is really bad).
" I’d rather she not spend a lot of time shopping around and “asking locals”."
You might be surprised how fast this can be done in Europe. Took my kid about 30 minutes to get her new Swiss number, and most of it was walking around the corner to the store. 
By all means, asking here is perfectly fine, but it makes more sense to buy her card there instead of tying to locate and order something here.
CM, I would encourage you or your D to google the expat sites as this issue is often covered. In general, it might be better to start with the larger operator and look for a cheaper alternative later. Changing SIMs and carriers is very easy. Most areas where tourist flock have stores selling prepaid cards. With an unlocked iPhone, the possibilities are endless. Most malls will have 1 or 3 of the main operators.
It really is not as complicated as it sounds.
Read the comments here:
Yes, we already spent some time googling and reading reviews (as well as articles along the lines of what you originally posted in trying to decide what general route to go) . And I already saw the tripadvisor thread (only one person actually recommended a specific carrier). No, I’m not expecting to buy one ahead of time here (though that would be ideal in my opinion) .
Oh well, just thought I’d ask.
If you have an iPhone, there’s no need to buy a sim card or other phone… Call your provider.
Verizon has a very affordable plan for most European countries. Call them one to two weeks ahead and tell them you intend to use the phone - there is an unlimited txt and voice, as well as pricing per voice/txt. I think it’s .99/txt and 1.49 over voice call.
I’ve never bought the unlimited plan, I just want to call our apt rental/taxi or shuttle, and maybe call a tour operator or two. We do txt each other - but sparingly - if we decided to split up.
Don’t remember the cost of the unlimited plan but it was reasonable. We just don’t use our phones that much while traveling.
Also - Verizon will switch you over to the local carrier, wherever you are traveling to. No need to do it yourself. Just tell them where you are going, and when.
I’m assuming other phone companies have something similar to Verizon’s. If not, they should. Verizon’s is very easy to deal with.
^ Well, the options one will have (among others) is to go with TDC (the largest operator) in Denmark:
http://shop.tdc.dk/on/demandware.store/Sites-Private-Site/default/ProductSetup-CreateMBBSubPage
or with a discounter such as http://www.lebara.dk/datapakker
Again, my recommendation is to go with the best operator for a phone service and a cheaper data for permanent use. For an extended stay, it is also possible to sign a temporary contract that is usually a bit cheaper than a prepaid.
In all cases, I would stay away from international vendors who promise to send you a chip with some data. Buying upon arrival is really simple and painless.
Sometimes I really want my phone working when I arrive, especially when it’s important for some people to have my foreign number right away. I’ve had great luck buying sim cards on Ebay. It takes a bit of research and sleuthing to make sure the card is specific to the country and legit. You can always e-mail the seller to clarify. I found a likely looking card with “three sim card Denmark” as a search. I make no guarantees, but I’ve done this for the UK, Italy, Argentina, and Spain.
We bought an inexpensive unlocked quadband GSM phone from Amazon before leaving the U.S. for use in Asia and Europe. The basic phone (non-smartphone) cost $17 and worked well with the SIM cards for the country in which we were staying. We bought the SIM card at our destination, and we found them fairly inexpensively, upon arrival at the airport.