Comcast (Xfinity) VoIP landline. When you call an AT&T Samsung Galaxy S23+ it doesn't ring and goes directly to voicemail.

user_fzu98c Hello! Thanks for creating the post and reaching out to us for help with making / receiving calls. I'm sorry that the call is going straight to voicemail. I know it's frustrating when you are unable to make calls. I would love to help and get this corrected for us. Are you calling the AT&T phone number from your home Xfinity voice phone line? Or is the AT&T line calling into your home? I have come across trouble like this from time to time when there was a recent phone number transfer between like providers. Was your phone number recently transferred? 

You are with the right team to have this corrected.