Can't receive verification code from my credit union on my landline

Credit Union recently added "Verification" when signing in to internet banking. When I request the verification phone call nothing happens. Phone doesn't ring. There is a normal dial tone. The call to me is an analog call. No texting or other cell [Edited: "Language"]. Credit Union checked and said there was something blocking their call to my phone and I should check with my service provider (Xfinity). Called customer service. Was told there was an approx. 20 minute wait time but could schedule a call back. Did that. Two hours later I finally called customer service back. Got a representative. She said my modem needed to be restarted. Since I was calling on my landline I mentioned my call would be cutoff. She assured me she had my phone number and she would call me back once the modem had restarted. That was two days ago . . . I'm still waiting for my call back!!!

Anybody have any suggestions? I have read every article I was able to find on my internet phone service . . . no resolution found yet.