Call centre with Voice over IP

A large number of call centre offerings have centred their attention around the use of Voice over IP. Most PCs although being designed with a multimedia capability fall short of being able to make a phone call. Just because you have a PC with a sound card, doesn't mean that you can converse with someone. Those that can, suffer from poor quality speech. A plethora of conflicting standards is not helping the situation. In contrast telephones are installed in most houses, are "ready to go" and are very simple to use. Just how difficult is it to dial a free-phone number?