Ive got an iPhone and i have been using Skype on it, and i have to say that the device that is used when using voip services makes a huge difference. When i used to use Skype on the computer using headphones there was not much clarity and a lot of disturbances. Since I have been using Skype on iPhone i have faced no problems at all and had no disconnection on any calls which I have made!

Is there any connection to using voip services with certain devices?