Wife's iPhone 14 goes directly to voice mail when I call her

Yesterday I called my wife 2x around 4 PM PST.  Both times it went to voice mail without ringing.  She has also had this problem in the past when others call her.  But she is able to call me normally, I have a Galaxy S24+.  Both phones are unlocked and have been on Xfinity Mobile for a long time.  How can I troubleshoot the problem?  Should I go to an Xfinity store and have them replace the SIM card?