From what I have been told (I have not experienced it personally), on incoming calls, the caller can hear the person at our end, but we cannot hear them. We can make calls via our internal VoIP with success it seems, but external calls are a problem.
Our VoIP provider ran a health check and they say that the SIP ALG is showing up as enabled. They also gave me a couple of ports to open, which I have created port forwarding rules for. I have also enabled the SIP helper on the router. The health check still shows SIP ALG as enabled. The phone itself should be configured correctly, as our VoIP provider configured this for us.