Terrible service at KFC ballito

I went to KFC ballito on Tuesday around 19h30 to buy meal for me and my family as I was busy with renovations the whole day and never eat. I stood on a que to buy which they had only 1 cashier that was doing till point and still go back to prepare orders. The cashier desapeared for at least 7minute, So I went and ask the lady that was seating on the drive thru as I could see her from the inside ,i asked if we should go and buy from the drive thru as that que seemed like a priority and she responded "the cashier is coming" and she kept quiet. I asked her to please get us another cashier and no response. I went back to the que and after sometime I saw the train was not moving and I went back in my car and drove to the drive thru which they had 2 staff there, please make me understand how this works, I wasted lot of time and I was tired, and I think you should know how many customers to expect in days where there are promotions or some sort.