You have a Samsung device. Their 2-step verification requires a text to confirm your login. You don't have to text anyone else or let them text you. You can most likely remove your phone number from your Samsung account and then your verifications will go to email or a pop-up notification on your device screen. The next time you receive a text from Samsung, you can block the number, but you are really being ridiculous by not allowing texts. You also have the option of disabling Samsung messages (if you have it) or uninstalling Google messages. You don't have to have any text messaging apps active on your phone for it to be a phone. The only thing Samsung will ever text you is your authorizations or issues with your account security, or if you specifically requested them to. They will also email you.
You should be able to block texts from anyone who isn't on your contact list. It's probably a setting in the messages app called "Block Unknown Senders."
You learned the hard way to never respond to spam, even to type "stop." That just tells them you're human and reading the texts. Just erase them and block the number.
As I said, they do not text anything other than verification of your login and, more often than not, they send a push notification, a screen card, and an email. I have never received a text from Samsung. If they are texting you advertisements or promotions, it's because you either opted in, or didn't opt out. In any case, you can probably reply with "stop".
