S7 Edge Messaging App Cannot Block a number that is not a contact

I can block a number that is a contact such as my mum. But I cannot block numbers by companies such as my network proviser Three. By block I mean stop receiving annoying text messages,  It is not Three I am trying to block just using them as an example. I cannot add three to contact to perform block options that does not work. What is even more infuriating is that I cannot find a number to block its just "Three" with no phone number to be discovered anywhere. How can I block these annoying text messages that are not even in my phones contacts. I am using the default messaging app on the samsung galaxy s7 edge, fully updated, no modifications made. Long pressing does not work either.