Agencies don't really care about the temps, they care about making money off the temps. So, if you happen to display an attitude, then they really don't care.

I know that when I worked with an agency I made it a point to get to know the person and we talked about business etc. I learned their name and always was nice and as a result they tended to call me first when they had a client. It's always important to remember, while people don't always remember exactly what you say, they never forget how you make them feel.

It's good that you are aware of how your attitude can make or brake an opportunity. You can work on changing that.