How can I cancel my appointment with apple store?

Hi there,

I am Sami from London. My apple iphone 4s was not connecting with my laptop. So i went to their one of store and they booked an appoinment for me for the next week. but I have solved that problem with the help of my friend. So now I want to cancel my that appointment with them. Can anyone tell me "how can I cancel my appointment with apple store?"