For about four years I received one SMS a day from a car dealer. No way to unsubscribe. Even calling them did not help. No idea where they got my number.
It’s cheap and easy to send bulk email or text messages. It is arrogant too. If the recipient is not looking for exactly that thing at that precise time, then you get a FFS response from her. Somewhere in her subconscious she stores a negative mark next to your company name. If you care at all about your reputation, get permission. The cost of bulk communication is huge otherwise.