I'd say it's a pretty rare case that a company would request that you initiate an interview call with a company: you call them, they have to locate the person who interviews you. Said person has to fire up your resume and cover letter on their screen plus whatever software they use to take notes - all this while you are waiting at the other end of the line.
- And what if your interviewer were stuck in an unscheduled meeting or at an interview whose time allocation was being exceeded while you are calling?
- And what if your scheduled interviewer got sick and the receptionist doesn't know who is the substitute who is supposed to interview you? It's going to get messy.
If the interviewer initiates the call, the interviewer obviously gets their logistics and their act together including going to the restroom beforehand before they call you. And the company is a lot less likely to look like the Keystone Kops. If I were them, they'd much rather call you while you are frazzled than you calling them while THEY are frazzled :)
As @DanNeely says, it doesn't hurt to email and confirm but my expectation is that the interviewer initiates the call.