For a phone number like this:
05 40 33 25 98
If you were to say it to someone, would you start:
zéro-cinq quarante ...
Or because phone numbers in France usually start with zero, just:
cinq quarante ...
For other cases:
01 42 05 50 50
... quarante-deux zéro-cinq cinquante ... ?
01 40 13 00 28
... treize zéro-zéro vingt-huit ?