How to make this sound more sympathetic and better, I'm writing a complaint to a company?

On the said date, I made the purchase of my new Iphone 6 with NKS assistance and headed towards the cash counter to pay for it. P was sitting at the counter, whilst NK was trying to put the transaction through and counting the cash I had given to him P comes out the blue snatches the cash out of NK hands places it on the counter and demands NK to follow him into a closed room. Whilst I'm waiting for someone to turn up and serve me again I'm left completely bewildered how someone could possibly interrupt a customer sale without apologising or excusing themselves.

When NK came back after 5min he looked very upset as if he was about to cry, I didn't take any notice and asked NK to give me the student discount deal, NK responded said he said he was unable to as ordered by P, he said he was scared to get shouted at again if he didn't hurry with the transaction (bearing in mind there were no waiting customers) I was really disappointed hearing this and didn't make me feel any better seeing Ps behaviour and aggressive facial expressions towards me, it made me feel very uncomfortable and humiliated. In spite, I insisted that NK does my student discount offer and made my word that I would complain about him.

(I will create another post with the missing paragraph, due to word limits)

After I paid for the phone I sat back down in the customer service desk and saw NK being shouted at by P, I heard him say 'hurry up and get rid of her' As soon as I heard him say that I told P to mind his own business and stop manipulating poor NK, he told me to shut up and that I'm very disrespectful and that he is NK superior and he owns o2 and he can do whatever he likes.

Just send in what you have written here.

Send it in just like that. They won't care or pay attention anyway. You're complaining that a manager told an employee how to do their job and got curt with you when you tried to intervene.