Poor customers service

Today morning,around 8:30went to kfc in montana,had the worse experience ever.passed through drive thru to order was told chicken will be ready in 5minutes and must wait close to the entrance and will get my food.did that because I was hungry and had hope that I will get my food,30minutes pass ,decide to check my food in the store,food my food on the counter .collected my food and left.to found out they gave me the wrong meal.called their customers service which they where not helpful,promised to get an sms to use at the desk to change my meal,which I received at 10 ,went back to change my meal since I only noticed when I was at work,the cashier gave me attitude,saying people who buy through drive thru are getting through her nerves since I was not the only complaining customers today,so im worried how Such a big company would not treat their staff good customers.