My app doesn't want to go to Read & write permissions



I have a big issue with my app: i want it to go from Read to Read & Write Permissions.

I’m in my apps back office, and when i do, i have this error message:
You must add your mobile phone to your Twitter profile before granting your application write capabilities. Please read for more information

Ok, but i’m in France, at Bouygues Telecom, and Twitter doest not allow me to add my mobile phone.

So i can’t use my app…

What can i do please?

This is a 2 months problem, and i still not have solution. Twitter doesn’t answer to me when i contact them…