To disable SIP ALG on a Technicolor, Thomson, or SpeedTouch router you will need to Telnet into the router and unbind SIP from port 5060. If you have a Telnet Client installed, you simply need to run the following commands in the command prompt, which can be accessed by pressing Windows Key + R, then typing cmd, if using Windows. If you are using Mac OS X or Linux, simply open a terminal window.
connection unbind application=SIP port=5060
NB: The IP address 192.168.1.254 is often the default address for this router, if a different IP address has been set on the router, use that instead.