I stumbled upon this gem about 3 months ago for a website I was doing. Bookly was the closest one. The issue with Bookly is that it's expensive initially and you have to also buy modules if you want to add more complexity. One thing that is not discussed really is the cost for sending a text. I want to say it was like $0.10/sms with them, which is how much it cost to send a text 15 years ago. Amelia does charge but it's a lot cheaper than that. I do wish we could have the option to use Twilio because their rates are SUPER cheap.
I have been in contact with support for the last 2 months on a feature I've been wanting to have and that is the ability to upload attachments with an appointment. I'm actively working on an orthodontic site and they want the option to upload x-rays for new patient exams and support messaged me back and said it is due in about a month, which is good to know! Amelia is a good deal even at the $59/yr compared to Bookly, but this deal is was more awesome!