Time management - conference calls

I was never concerned about how much time I spend on the phone, it seemed not too much. But this week I've noticed that I was slightly behind the schedule for some of my deliverables. Just checked my calendar and found out that each week I spend 8-14 hours on conference calls, 10 on average. That means that my work week lasts less than 4 days, and I plan for 5. I am doomed!!!