If you are looking to stay in touch easily, one option is to switch to an iPhone and iMessage. If most of your friends are on iOS devices, they will still be able to reach you, as iMessage works on the basis of connecting people based on who the are.
"Link your mobile number to you Apple ID and your messages still reach you, regardless of which phone number you're on. A second idea is to start to use Google Voice before you leave and get free text messages anywhere in the world; plus, by having the Google Voice number as your phone number, you get your voicemail. You can also use services like Facebook Messenger, WhatsApp, Viber, and Telegram to get around the cost of messaging and have more features," says Abramson.