Why am I getting a message that says I am roaming when I place a call?

Error2023

When I try to place a call I get a message that says "You are roaming, to call your mobile carrier or any other phone number, purchase a calling pin by pressing 1 now. To make a collect call to a mobile phone or a landline phone dial 2 now" and I cannot receive calls. However, in the network settings it says I am "Not Roaming". In addition, I can send and receive texts and access Data using the phone.

This question has been asked three times in the past (2014, 2018, and 2020). A lot of people noted they had the same problem. I did not see an answer in any of the other threads.

I have three older Iphones (an Iphone SE, Iphone6SE, Iphone7SE), which I have had for several years. This morning, the oldest of the three (the IphoneSE) started giving this message. The other two phones are working just fine.

Error2023

I stopped at the Verizon store, and the person their was able to quickly fix the problem. He switched roaming to "on" under Cellular settings, and the phone started working. He thought the problem may have been related to shutting down the 3G network, and said something about changing a setting for 4G. I later turned to roaming back to "off", and the phone continues to work.