Using mobile phone in France

Qashqai66

Hi All, I am hoping someone out there can answer this question.  My wife and I have never quite got the measure of using a mobile phone.  We have a basic phone on which we make about two or three calls each year and send the very occasional text message
to our family when in France. When we use the phone in France to a UK number we have found that we do not have to put in the international code as it simply dials the correct number automatically.  I have been wondering what might happen should we want to
call a camp site in France while we are there. Should we put in the internationa code for France in order to get through?  All answers greatly appreciated.