The three letters that define much of the world's wireless capabilities are GSM (Global System for Mobile Communications), a big, seamless network that makes for easy cross-border mobile phone use throughout Europe and dozens of other countries worldwide. You can use your mobile phone in France provided it is GSM and tri-band or quad-band, just confirm this with your operator before you leave.
Using your phone abroad can be expensive, and you usually have to pay to receive calls, so it's a good idea to get it "unlocked" before you leave. This means you can buy a SIM card from one of the three French providers: Bouygues Télécom (www.bouygestelecom.fr), Orange (www.orange.fr), or SFR (www.sfr.fr). A SIM card with 5€ call credit costs about 10€. Alternatively, if you're phone isn't unlocked, you could buy a cheap mobile phone. To top-up your phone credit, buy a Mobicarte from tabacs, supermarkets, and mobile phone outlets. Prices range from 5€ to 100€.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.