Actually (with restriction) it's work like that :
- when you can send message = button is visible
- when you can't send message = button is invisible
I would like to have :
A button "send a message" always visible, even for people who can't send messages.
And for exemple when they click on the button there would be a message inviting them to switch to a Premium Account.

I am in the way to solve this problem but I would like your opinion