If it seems like you're receiving no calls, first make sure your status is set to "visible"!
The next way to ensure you receive calls, especially if you're a new tutor, is to sign up for a Priority Hour. When you're on a PH, we will automatically direct students' calls to you. Without a PH, you'll only receive calls from students who search for skills/experiences listed in your profile and then choose to call you specifically.
If just one student can't call you, check out this article for more information about why that might happen.