If you have any problem with VoIP, especially, the problem of latency, your ISP and your broadband package may be causing factors.
Thing is, most ISPs offer you packages with nice download speed but may not give you good upload speed. Most of the packages may feature upload speed which is just one-tenths of download speed. This will definitely affect the voice quality.
If you are still a dial-up user, take note of this point.
