I have yahoo phone in and phone out service but the quality of the head phone and mic is not the best. Can I use a skype type internet phone to make and recieve calls on Yahoo Messenger?

I signed up for Verizon's phone and wireless internet last year for a special price, and I also signed up for Comcast digital cable (with the box) because it was a first year special price. But now both of the first year deals have run out and I want to do all three with either comcast or verizon. Which would be an easier switch?