Fake bookings and fake calls for bookings

I do not know if other guest houses have experienced what I have been experiencing

This is now almost 2 years I have been managing my guest houses and since the way go, I notice many bookings on booking.com but who turned up as a no shows, not only that, I receive in average 10 calls per day which turn out to be fake, they pretend they are on their way to the guest house but then no one arrives, before they made me keep the room for them but only not to show up, now I have changed the policy of asking a deposit before they come thinking it will deter their calls or bookings but with no success so far, I think there is or are guest houses who want to fail or go out of the business, every day is the same story, now there are sending people straight to the guest house and ask for the room, once they come inside, they find excuses not to stay when they could check the rooms online before they come. Does any of you have similar experiences? How did you deal with this threat? I want to hear from you