how to block sms when menu doesn't show in messages

[Android Central Question]

When I receive some text messages in the standard Android Messaging app on Samsung s8 (no root) a name will appear instead of the mobile number that it comes from.
These messages are spam and I have my phone number on the do not call register.
The message will come through and only have the "delete" option at the top right, there is no menu option there to block the sms.
These messages also don't have the ability to reply, whether they have how to unsubscribe or not, which is really weird.
I've checked viruses, malware and my phone is fine with everything else working fine, just can't work out how to stop these from coming through.
It doesn't have a phone number for me to add to the block contacts option, and the name that is provided instead of the mobile number is not in my contact list, so I cannot block them via that way.
I have tried everything, anyone have any issues? Any help would be appreciated so much!
I would provide a screenshot, but can't see where to.

 

[Dano1200r]

Press the volume down and power at the same time to take a screen shot.

 

[B. Diddy]

Welcome to Android Central! Open that conversation and tap the menu button at the top right, then People & Options. Does it show a number there?

 

[Gayle Lynn]

Press the volume down and power at the same time to take a screen shot.

Or swipe if that is enabled.
Another option: BxActions - remap the Bixby button to Take a Screenshot. Do it a lot so handy.

There is some support for blocking numbers not in Contacts.
You can block phrases.

Scam phone callers can fake your area code and prefix now in attempt to trick you into thinking it's someone local.

People will pray on people. Buy calling lists, Even th then hit them with a request. One reason I avoid political donations. Theyll sell your information.

Scammers use the Do Not Call Registry! It'll only get worse.