Desperately need help for my elderly father

I just spent north of 90 minutes on the phone with Xfinity customer service and basically got nowhere. My father has had some serious health issues of late and had to move from his residence in Pueblo West, CO. I'm attempting to cancel his internet service but keep his mobile intact and move it over to another existing internet service of his. It's critical his mobile service remain intact through this process and his number not change, even temporarily, due primarily to his medical providers needing to reach him. I have full authorization on both accounts. Is there anyone that can help? It feels pretty hopeless right now and I need to get this solved for him asap. Thanks in advance.