我想以一封英文投訴信去投訴間戲院點寫呢?幫我寫啦,THX..!

First, why English if you could write Chinese and the staff of that movie theater would understand?
Second, please give more details about your complaints:
間戲院有人吸煙,有人大聲交談,無視警告, (you mean some staff had given those people a warning or it was just the "No Smoking" sign.)
售票職員得一位又要人多點睇戲呀? (you mean too many people were queuing up and the staff member didn't sell tickets fast enough so you missed the first part of the movie? or the theater was full and it was too noisy to watch the movie? (you can't complain just because the theater was full (!) but that people were talking too loud and there was no one to stop them.)

Anyway, let's see:

Dear Sir,

This is a letter to complain the poor service provided by your movie theater.

On June 1 (please amend), I was in Theater A (哪一院? A院? B院?) of your movie theater watching Pirates of Carribean (please amend) between 7:30pm and 9:30pm (please amend). During that time, some members of the audience were smoking and talking so loud that I could not enjoy the movie itself. What frustrated me the most was that there was no one to stop them / that there was only one staff member in the theater and he could not handle the situation alone. The nightmare last throughout the playing of the movie and I left the theater in disgust.

I request your follow-up actions. You may contact me at (phone no.or email address) for further details. I look forward to hearing from you.

Sincerely,
ABC