Looking to travel with my wife in Germany for a week, Spain for 10 days, and UK for 5 days in 2 weeks time. We both have iPhone 4s with AT&T that are out of contract now and can be unlocked. Question: She starts in Germany and heads to Spain. I start in UK and head to Spain. We both then go back to UK. Is there a good SIM I can buy online that allows us to use voice, texts, data in these 3 countries that I can get before we leave?