Web phone wanted by VOIP company

We are a VOIP company and we want a web phone and softphone for our website and costumers PC where the costumers can dial any number from their VOIP account. Also when the costumer signs up for a new account from our webpage and they get a confirmation email, if possible we would like the web phone to be embedded in that email, so that they can starting making calls immediately. The web phone and PC soft phone should have our IP address pre configured with our logo and so on. The costumer should only need to put in their user name and password.