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.
Learn more about SIP ALG in our knowledge base article here: SIP ALG
Log in to your router's management interface, then select System -> Conntrack -> Modules -> Sip -> Disable
If your management interface is not available, you can perform this change from the command line by logging in, then entering the following commands:
configureset system conntrack modules sip disablecommitsaveexit