How to get a free phone number

If it exists!
However, your number will be in "VoIP", so you'll need a software (like X-Lite).
You will be able to call numbers starting with 01, 02, 03, 04, and 05, and you will have a limit of 10 minutes per month. (you can contact the manager to see if you can increase it)
You can also share your number with others so they can call you for free from a landline.

Go to www.numbox.fr
It's free but limited ;)