Automated Vivian text alerts for "hot" jobs are sent via 68773- you can respond STOP (with no other words or punctuation marks in the message) and a confirmation text should follow that you have been unsubscribed. You can also respond STOP to any existing conversation that you have with a recruiter to archive that thread and prevent them from responding.
If you're still receiving job proposals after responding STOP multiple times, it is highly possible that you still have your job search toggled on, therefore making you appear 'actively looking' to recruiters. Check this article out for instructions on how to turn your job search off: How do I put my search on hold?
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