I posted the above post. After spending several hours on a chat session with an agent with my carrier (Verizon). I came up with the solution to the problem. I have on both Iphone 11's a "Call Filter"app with Verizon. I am signed up for the free version. I like the idea of being told that some calls are potential spam. I read the fine print and it stated that some calls that are in your contact list may be sent to voicemail. On the Account page, go to the bottom and click on "Recent". There will be a list of telephone numbers that have been sent to voicemail. you can select any number click on it will stop the number from going to voicemail. Also go to Block Management in the Call Filter app. In the Block Management, tap on "Allowed." You can add up to 5 telephone numbers in the Allowed section with the Call Filter Free. If you want to add more telephone numbers It costs $3.99 a month. I am satisfied with the free version. The most important point is, "I know what was causing the problem on my Iphone 11. I hope this will help anyone else having the same problem. It would be great if the Verizon and Apple techs knew this is what causes the landline calls going to voicemail. I am sure this is the problem with other Call filters or Call Blocks.