Texting app that doesn't need Wi-Fi?

I need to find a texting app that doesn't need Wi-Fi. I'm from Canada and am going on a trip to London England and want to be able to talk to my boyfriend while I'm away for a week. I don't want to pay for a messaging plan for my phone while I'm away and my boyfriend doesn't have access to Wi-Fi. We both have iPhones. Any suggestions would be greatly appreciated!

Then you won't be messaging, unless you can quickly find a way to transport messages through dirt.

1/2 Right. Facetime and iMessage do both work on Wi-Fi or data. What I think you are confusing is you and Boyfriend don't have to be on Wi-Fi at the same time for those two features to work. So, yeah you can be on Wi-Fi texting or Facetiming in the UK but the messages and face will still get to him even if he has Wi-Fi off and data turned on. Just don't voice call from there or the bill will be so high you'll never come back due to the debt you'll owe. Wi-Fi on Facetime or iMessage for you, period, him, it doesn't matter. He's home. Test it out that way before you leave to see. Best luck.