Working from home issues

Hi - I work from home and often have calls drop with our phone provider Hunter. They sent me suggestions of things to check for and have no clue where to start. When reaching out to support, he told me our internet looked fine, reset the modem and then tried to upsell me on internet that would cost me $200+ a month. 

Suggestions from Hunter Phones: 

I believe it is a (SIP) signaling issue. A soft phone can be up and registered but may be missing the signaling that allows it to pick up calls. This could indicate an issue with the user's home network.

Possible causes

• ISP (internet service provider) provided routers often have ports blocked and SIP ALG enabled.
• SIP ALG enabled or any other special firewall rules on the home router.
• IP addresses blocked by router firewall.
• A firewall on the computer.
• A VPN connected back to the work network.
• A DMZ on the router.
• A wireless internet connection - if it is wireless can it be hard wired to the router.

Any help with how to troubleshoot would be amazing!

TIA!