646-791-3070 This Number keeps Texting me Questionnaires that I Have Never Requested in the First Place.
    I've Blocked this Number on Several Occasions; & somehow, this Number or Similar Numbers Still Keeps Sending Questionnaires by Text.
    I've Even Texted STOP & to No Avail, it Doesn't Help.

For text messages: forwarding any text message spam you get to the short code  “7726,” which spells “spam” on most phones, to alert your network operator to the abuse. ATT won't accept 7726 But they will accept BLOCK and return a message that the web site is blocked. forward the texts to 7726 or BLOCK, depending on your phone carrier.
http://www.att.com/esupport/article.jsp?sid=KB115812
https://www.consumer.ftc.gov/articles/0350-text-message-spam

I  just found this out regarding this Number 646-791-3070:
1-646-791-3070 is not a valid number. If you are sure that you got a phone call from a number beginning with this prefix, the caller may have 'spoofed' caller ID.