Note that as this process may temporarily interrupt your internet connection and phone service, we recommend doing this in an off-peak period or outside of business hours.
Disabling SIP ALG
From the Sonicwall main menu, select VoIP, then choose Settings.
Find the setting for SIP (or SIP transformations) and uncheck, then check Enable consistent NAT and choose save.
If you're prompted to reboot, please do so.