Letter "R" next to the network bars

This means that you switched from your operator's network, about which we know nothing, to another network... for example, Free had a partnership with Orange, so if there's no Free network, you switch to the Orange network... the same applies if you leave France and your operator has a partnership with a foreign operator when you go abroad, etc. So either you disable roaming and see if you connect back to your operator. Here’s an example, and that’s the principle... and obviously, if your plan allows it, otherwise no more calls... Also, are you not in airplane mode? Do you see your signal bars or not?

https://forums.cnetfrance.fr/topic/172350-android--desactiver-le-roaming--itinerance/

Since you are not responding to the suggestions, it’s difficult to help you... Have you disabled Roaming R, then restarted your phone and checked if you are on the Free network? Do you have signal bars? Here you can see the network outages for Free. Maybe that’s it...

https://www.universfreebox.com/article/40216/MaJ-Free-Un-incident-reseau-touche-actuellement-une-partie-des-abonnes-du-nord-de-la-France