My phone will work when I set the firewall security to low but it won't fully work when it is set to high. Is there a way to fix this? Oddly, I can make and receive calls on high security but once either side picks up, neither party can be heard.
What you are experiencing is very typical and normal. On the "high" setting your router is more strict about which ports it lets traffic pass through. Unfortunately, how you go about changing it is dependent on the router you are using. It's likely that you will need to engage someone who can look at your system and determine how to configure the router. With some home routers your only solution may be to leave it set to "low".