I am having a similar problem with a new Pixel 4a. I cannot make or receive calls or text messages, and accessing the internet works only sporadically. When I 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." My network settings tell me that roaming is disabled, and the other line on my family plan works fine.
We want you to be able to use your phone without any issues, C00p4w. Let's take a closer look into this. When did this issue start? What signal is showing on the phone when this happens? Has there been any changes to the device when this started such as new updates or apps?