If you have a reliable internet connection, you can use Skype, Zoom, Google Talk, FaceTime, Snapchat, Facebook Messenger, and other internet-based calling platforms to make free calls to both landlines and mobile phones. TimeAndDate.com is a useful website for calculating time differences, international calling codes, and other travel information.
Some phone service providers have affordable temporary international plans; check with your provider for options. Some students purchase a cell phone or interchangeable SIM card while abroad, which provides an easy way to stay in touch with friends at home and in your host country.