Hi Dan,
You should be able to either dial French numbers in their national dialing format (leading zero included), or use Verizon’s instructions and dial +33 followed by the French number without the leading zero this time.
Examples:
06 xx xx xx xx
+33 6 xx xx xx xx.
Both dialing sequences above should work. The second option is basically the international dialing format of the French phone number, but GSM technology these days is advanced enough to know that you are in fact dialing nationally. Of course, the good thing about using +33 is that the number stays unchanged no matter where you are dialing from.