Ethernet device, no inbound traffic

Recently switched to xfinity. I work from home and my phone is to be plugged into my router or modem and computer. The phone makes outgoing calls but does not allow inbound traffic. No incoming calls unless I reset the router and it works for 5 mins. My IT team states this is due to the provider's advanced security team. I called comcast 3 times and have been hung up on every time.