“Report junk” does jack all for legal to semi-legal spam, thanks to the carriers fear of politicians. It might do something for phishing and unabashed scams, but for the bulk of spam you get you do want to reply STOP. Not because the campaign will stop spamming you, but because evidence of explicit nonconsent is the only thing spam gateways like Bandwidth.com actually care about (under duress from the carriers), and they might actually fine them $10. Or worse, threaten to rate limit their spam.