VOIP Ports

I am not sure where the issue lies but figured I would try it here.

Been working from home over the last two years and phone call quality via a softphone generally was good.  I could hear the person crystal clear but occasionally, my voice would be garbled like it was being compressed.  This seems to be happening more often now.  I do understand the network is getting hit a different way now that all the residential customers are working from home so not sure if this is the problem.

Currently connected via VPN to corporate office using Cox  HSI from home.  Have reset my modem, reset my router, even set up port prioritization for VOIP systems, along with restarting my Win 10 computer (where VOIP software is installed).  Decent download speed of 50-90MB/s and upload speed of 10MB/s with a Latency of 9ms

Our IT department have not been able to find anything on their end for a cause and each time I call my cell from my voip line to leave a voicemail, it sounds perfectly normal.

Are there specific ports that handle the outgoing call vs the incoming call, or do they use the same port?  From what I am seeing the only port that is used could be 5060.

Thanks,

Mark