Call with the form

Software
Your phone number
The number of your correspondent
your user name
Your password

Direct call from a Web address

You can initiate a call directly from a Web address. 

http://progx.ch/home-voip-call-3-1-23.html?provider=PROVIDER&tela=TELA&telb=TELB&us=USERNAME&ps=PASSWORD

PROVIDER Replace by the provider (for example justvoip.com or netappel.fr)
TELA Your phone (for example 0041793232369)
TELB The telephone of your correspondent (for example 0041264754424)
USERNAME your user name
PASSWORD Your password

Example :

http://progx.ch/home-voip-call-3-1-23.html?provider=freecall.com&tela=0041793232369&telb=0041264754424&us=progx_45&ps=pfGbvWe