My number is no longer assigned!!!

Hello, here’s my issue: I just realized that when I call or send messages, a different number appears on my interlocutors' phones. When I check my SFR account, the same number is listed. When I try to dial my usual number, it says that the number is not assigned. I've been with SFR for over a year with a plan, and no changes have been made since. What do you think? Will I be able to recover my correct number? Thank you.