How not to lose my temper?

Hello All, I hope someone out there can possibly help me. I've been losing my temper lately and it's affecting my work. I get upset with the slightest thing..... You see, I'm getting short with these people that I know not from work for for the work purpose. They ask me the same questions day in and day out, they don't know their insurance, they don't know what their insurance is, and they don't seem to understand that in our office we do not give out private information regarding anything of any sort. They continue to push and push and push and push until your buttons are ready to explode. There's no respect over the phone when they call, namely none at all. So, I'm getting very frustrated and I don't know how to handle this problem!!!! Please only serious answers...... Yes, I've seen a psychologist, she tells me it's not me, it's the people around me