Text Message not received

Hi - my work is asking to verify who I am by sending a text message to my phone. The phone number in the website is correct but I am not receiving the text message.

I am guessing that maybe I blocked that sender at some point in the past? When I go to my blocked sender list in the message app there are hundreds of numbers.

Is there a way to figure out any more information on this list? If i unblock them all I cannot imagine all of the junk messages I am going to get - but is that my only option?