I use Agoda all the time. I think I know whats going on. Also, to someone who suggested using Booking.com, realize the are the same company. There is also a setting on Agoda to show all fees + taxes.
Many of the Agoda hotels are Pay-When-You-Stay. My guess is the OP did not book a pre-paid reservation.
When you arrive, the hotel is supposed to tell Agoda that you stayed, and at some point, the hotel has to pay Agoda their commission. If the hotel does not reply to whether the guest stayed or not, then Agoda would not charge anyone. As for how the hotel can keep doing this, this hotel has apparently squeaked thru the cracks.
I've had one or two of these "no credit card required" bookings that I made on the wrong day, or I just plain missed, or left early, and there's never been a charge from Agoda.
Probably since you complained, they might not be listed anymore.
Also, if folks don't mind jumping through a few hoops, if you use Topcashback.com, you can get 6% back on your Agoda and Booking reservations, but you have to use a browser to get it. You can't use the app.