Stop Text Messages

I accidentally signed up for text messages from Auto Payroll and can't opt-out. I've tried STOP and UNSUBSCRIBE, both of which reply with a message stating "You've opted-out of texts from Auto Payroll and will receive no additional msgs." However they keep coming, sometimes several in a day. I tried chatting support and after 45 minutes with "Cherry Ann", she just disappeared. I can't just block the number as it comes from 87027, which is used by many companies for text messaging that I may need to get in the future. How can I get this turned off? It's actually illegal not to allow a recipient to unsubscribe from a text messaging service, so I'm looking to get this resolved ASAP please. An example is attached but this has been going on for over a month now.