Blocking text messages from unknown callers

Hello Frankd. It seems the process has changed a bit but I think I've figured it out. First, open the Messages app and locate the unknown person you wish to block. Double tap on their message to open it up as if you were going to respond to them. Next, locate the back button in the upper lefthand corner and swipe right once. This will take you to their name.
Once you find the name, double tap that. This will open up an area which gives you some options.
Next, swipe to the right until you find the Info button and double tapp to open. This opens the Details for the person. However, in order to edit this person to block them, you must locate their name again. The Done button is located to the left of their name. Locate the name and then double tap to open.
Finally, at the bottom of the items is where you will find the Block This Caller button. Double tap to turn it on.
Use the Back button once to return to the previous screen.
Now double tap on the Done button and then use the Back button once more to return you to the main Messages list. From here you can completely delete the message if you wish. this doesn't remove the block you just placed on the caller.

HTH

Hello Roxann,
Thank you very much for your help. Unfortunately, I have already deleted the spam text that triggered this question but I followed your procedure for a known contact as a test and it worked perfectly.I don't get many spam texts so it's a case of use it or lose it! The procedure seems a lot more complicated now. I guess it must have changed with iOS 12.
Once again, thank you very much for your help.

I'm not certain when this was changed but it certainly takes a few more steps than it used to. Glad it's working for you.