Is it appropriate to call professor? I exchanged an email with a professor on Thursday and he asked me if I am available to call him on a specific time next Monday. I replied the email to confirm the time but no reply from him. Therefore, I resent the email on Friday to re- confirm that he knows that I will make the call. However, no reply as well. So I am wondering if it is appropriate for me to call him at the time he indicated next Monday even without his reply?
Sure. You have booked a time, make the call. If you want to be sure, ask him over the phone if it is still a good time.

Academics are busy and slow responders, so since you confirmed your emails may have been given the lowest priority.