When you sell to hotels, the strongest opener isn't about your product, it's about the commission they hand to online travel agencies every single night.
The signal
Scrape which OTAs a hotel is listed on (Booking.com, Expedia, and the rest). Being listed is public, and it implies a painful, ongoing cost: 15-25% of each booking.
The angle
"Noticed [Hotel] is listed on Booking.com, want to reduce your reliance on OTAs and the commission that comes with them?" You're naming a real number on their P&L, not pitching software.
For a WhatsApp-booking client, referencing the hotel's actual OTA listings and framing the offer around direct bookings made the outreach immediately relevant to the person who feels that cost every month.