If your iPhone sends text messages from your email address
With Messages in iOS, you can start conversations with your phone number or with your email address. Set your preference in Settings.
Use your phone number to start conversations in Messages
In the Settings app, tap Messages.
Tap Send & Receive.
In the "Start new conversations from" options, tap the phone number that you want to use.
New messages now come from your phone number. If you have existing Messages conversations that you started with your email address and you want to use your phone number instead, you need to start a new conversation.
Learn what to do if you can't select your phone number in the settings for Messages