How do you change your telstra pre paid mobile phone number?

I gave my phone number out to a guy from the dating site. He rang me and he is not my type of guy. He keeps sending me text messages that I am getting sick of. I don%26#039;t think we will get on but he wants to meet for coffee. I want him to stop contacting me. How do I change my number?|||Go to a telstra shop they will help you ~~