How do I stop the harassment?

I started an online quote request with this company in June and I have regretted it almost daily ever since. I discarded the online quote form because I decided they would not be right for me after all, and then the harassment began. First, I received a completely unsolicited and unapproved phone call from a sales agent within less than 10 minutes of discarding the form. My phone number had already been filled in so they obviously save the details of even a partially completed form (VERY poor business practice) and this random agent was suddenly babbling in my ear about wanting to complete the enquiry with me. I told him that I had no interest in that at all and that I did NOT approve any contact requests so he needed to please remove my number from the system with immediate effect - which I have every legal right to request, and it MUST be done in accordance with privacy laws. Clearly, he didn't, because I've been harassed by 1st for Women almost every day since then. I'm being inundated with spam texts from them - literally almost every day. It is driving me mad and making me VERY angry because they have absolutely no right to be doing this.

They've also clearly sold my number to third-party advertisers because various other spam streams started at exactly the same time, and I don't believe in coincidences, especially since my number wasn't given out to anyone else at that time.

I've opted out of the texts around 17 times and emailed them directly at least 3 times - no response and no change. They just ignore me, but keep texting me!!! I've had the same phone number for 20 years but I'm on the verge of changing it just to get away from 1st for Women's constant harassment. This is utterly ridiculous and totally unacceptable.

I DON'T WANT ANYTHING TO DO WITH YOU - NOW OR EVER.