I've got two main issues with this app. First is that it has not been updated for iPhone X and up. The top and bottom have black bars.
The second is that it is very tedious to find appointment times. I have to search a date range, select a day, select a procedure, and I then have available times displayed. Guess what, if there are no times available, now I have to click the back button which takes me all the way back to the date range search. Just make the process easier, list all available times in a scrollable list and have a separator per day.