A little background: I'm a tattoo artist and recently changed the way my online booking is set up. I now have it where each service I offer is listed as a flat rate of $50, so that clients have to pay that as a deposit when booking. When they check out, I go in an add their remaining balance and have them pay that. 

But I'm running into a problem. Here's an example. Today I had someone who paid the $50. Their appointment took longer than expected, and when I went to their appointment to add the remaining balance and check them out, the appointment showed as completed already. So I'm assuming what's happening is that if they client is booked for one hour, and it's not showing a remaining balance to pay yet (I didn't put in an amount because I wasn't sure how much the session was going to be), the appointment auto-completes at the 1 hour mark. 

I need to make that NOT happen. I need to be able to mark the appointments completed when they are actually completed, as this also helps me with keeping track of my time with my client as well. Any ideas?