This was our worst experience ever.
We reserved this tour over a month ahead of time through Viator which apparently though was through a third party called VIPTOUR. We got the instructions of where we should wait for pickup and no one came and VIPTOUR did not answer their listed phone nor to messages via the app. We drove to the Navajo tours and they found out who our reservation was through and when we called them and drove quickly to their office we were two minutes late so we missed our tour and no one cared enough at Antelope Slot Canyon Tours to help us in any way although we were late through no fault of ours. We do NOT recommend these people either. As we got to this operator, VIPTOUR finally called us back but by this time they could not do anything either except apologize.
Note to anyone: Do NOT reserve a tour through VIPTOUR (who is simply an aggregator it seems like) and consider not using the actual operator Antelope Slot Canyon Tours as their customer service is non existent.
After all this, we drove back to the Upper Canyon start location and reserved a tour with the Navajo tribe for the next day.
That tour was wonderful and 2/3 of the price through Viator. Anyone can sign up with them even on the same day.
Viator should drop all third parties and work only with actual tour operators and, in my opinion, only with tours operated or owned by the Navajo Nation as they need all the help they get after COVID.