VOIP integration into PHP + AJAX coded DATABASE

Hi everyone, i am looking for someone who is experienced in integrating VOIP based software into a custom made web based program that i have. This program is basically one of which is based on clients phone numbers but i would need the ability to fuse the VOIP program into the databse containing the clients phone numbers so that my sales staff when they call the clients through the program they would not be able to see the phone numbers. This is done so that they do not copy the phone numbers. I would expect the program to be very simple to use. Any direction would be much appreciated. Looking for someone who has any custom built VOIP software. Any knowldge of integrating VOIP software Would prefer cheap calling rates and good quality VOIP communication software. Mainly suitated towards Australia and New Zealand. Please send screen shots of what you have and what you can provide. Bid is negotiable.