Receiving unwanted SMS and tried to do the opt out thing but they won't stop.

Like most Government departments, all bark and no teeth most likely, but worth a try.
Report spam to this site. http://www.acma.gov.au/theACMA/spam-report-spam

I'm getting texts from 'OfferFind' asking me to test Nike Products at all hours. Not sure how they're doing it but the text doesn't have a sender number, rather it asks me to text 0481 073 232 to STOP. Or to follow the link: http://ta-p.co/L5Hb to take up the offer.
I am super careful with providing my phone number but have recently shopped with Booktopia and Book Depository both of which asked for my number. How do we report them or block them?? SOOOO angry at being woken up at night and disturbed at work.

Crap !!!!
What part of annoy they don't understand

Yes - i am getting these too. If anyone finds out how they acquired our numbers pls post. I have someone to go visit them...

First my mobile, now my wife's and you can't use "stop" they want you to ring another phone number for them to stop sending

they wont stop

spam

Sending me text from OfferFind. I cannot block the original text. but has this number to reply Stop too. I am not sure if this will stop the harassment though.

These people are spamming me. They sent a message to "Opt out" now they send more messages & it's now costing me.

How do I stop this constant harassment?