First and second round interviews from 3 companies, need to calculate risks

After I set up a phone interview for Company A, I received a phone interview request from another promising, large Company (B.) I rescheduled my phone interview with A so I could prioritize B. I just finished my phone interview with B and they want to schedule an in-person interview. The next available slot is when I rescheduled with Company A. The next slot is next week. I also received an email from another Company (C) to schedule yet another phone interview.

I'm hesitant to reschedule again with A since I don't want to look unprofessional and unorganized, but I also don't want to pass up a chance of getting my foot in the door quicker with B. I'm waiting to hear back from Company C on a time.