Charging per second - pathetic

I made an apt for a cleaning for my 3 year old son and for myself for 215pm. I received a text which I didn't notice was 1 of 2 that was a reminder for my 230pm appointment. So my son and I showed up at 220pm. I checked in and they told me they would be with me, we sit down and then a lady comes a few minutes later and tells me that I'm late so they can only do 2 checkups not cleanings. They were far from attempting in anyway to be sympathetic or accommodating and there was no one else in the waiting room. I didn't come to the dentist for what they consider a "checkup" (thank goodness as my friend told me today this very same place took her one cleaning dental apt paid for by her medical aid and only gave her a 5 min "checkup" aka looked at her teeth and said they were fine, and refused to allow her to just pay for that and come back to use her full medical aid credit because she booked "checkup" online and like most of us figured that meant the full service/cleaning and all.) I told them rather do the "checkup" and cleaning for my son rather. He was in the room for less than 15 minutes and they charged us R770!!! For a 3 year old cleaning?!? For less than 15 minutes of time?! What a *******. The dentist was very nice with my son so I won't give it 1 star but I certainly will never go back there. They apparently care more about charging by the second then customer service. Very disappointed.