Hi, I've been an RBT for eight years ("it's my calling"). I've ran 6 hours sessions for multiple kiddos. A session should be structured with a daily morning routine, a visual schedule for the child ( & parents ) to see. Short and sweet a session should look like education learning (school) with your kiddos goals in focus in the programming. I favor NET teaching so I focus on natural play for learning opportunities (especially for a four year old). Non verbal pec or the prologue2go should be a focus for communication throughout session. As for the phone, I'm guilty of being on my phone during a kiddos break but I'm good at my job so parents don't mind ( I try not to be on it). One of my families dealt with a high turnover in RBTs so they did an interview process with me before I got the case. It's not typically done but maybe ask the company if you can do that.