the way to cancel a pandora account varies depending on what device you have it on
therefore i am going to give you this webpage which gives instructions for each device and how you purchased it.
if you need further help please just let me know and i will help you with it.
btw I do not work for pandora. I am an independent contractor that works for the justanswer site helping people with a wide variety of computer related questions and i take pride in helping them. I only receive credit if the customer is happy that i have given him the correct answer and solved their problem. I can not solve any problems with pandora itself but i can certainly help you cancel the service. I hope that you will give me an excellent rating when you have done so.
if you did not see the link above here it is again