Messages App draining battery iOS 11

I’ve recently upgraded to a brand new iPhone 8. Noticed my battery has been draining excessively... fully charged overnight, dead by 2pm.

I’ve turned off background refresh.

I’ve set location services to never use messages.

I’ve had the phone in low power mode since taking it off charge.

I’ve deleted all gifs /photos and videos attached to messages.

Despite all this messages has had 18+ hours background time in the last 7 days...

Please help me fix this.