Help setting up Phone VoIP System on Arris router

So I have a company router that’s old and was setup prior by another technician and the company I work for is switching ISP.

So we are no longer using ISP & Router A and we are now using ISP & Router B.

Everything in A is setup to allow full Wifi and connection to the internet and the VoIP called MegaPath works.

With B, everything works with Wifi and full connection to the internet but I can’t seem to get the right settings for the VoIP to work. Such as the In/Outbound’s & UDP’s & Protocols.

If anyone has done this before, especially on a Arris. Please comment and help me.

Also I was thinking in the future to upgrade the router to a better one that’s both provided by the ISP or pay monthly for a service from MegaPath that runs our phone system with 24/7 support plus you pay for a nice router monthly that gets replaced if broken or fails.