Apart from meeting in person, speaking to partners “on the phone” is the most direct way of communication. Video calls can be an exciting and fun way to get to know partner teachers and students, to plan the project, to present results to each other, etc.
If both partners establish a Skype account, you can call each other for free. You need to have an integrated microphone option on your computer (most have this option) and if you want to use the video-conferencing option you also need a webcam (integrated in more modern laptops). Video-conferencing allows you not only to hear your partners, but to see them as well.