They sent you a confirmation email when you signed up that lists the phone number. Just use that number from that email. I just cancelled, and it was easy. Just put cotton in your ears for the 45 second spill they will give you concerning how important it is to keep it.
Starting Score: 583 EQ, 612 EX, 569 TUWell, I have a little trick to get the reps off of the phone, but it is so bad. When they asked me why I wanted to cancel the free trial I told them that I was planning to buy a house with my wife, but I just caught her cheating on me. You should hear them just freeze! I cannot imagine what is going on in their minds when I say this to them, but it works! They bsically just thank me for using their service and ask me to keep them in mind when things get straightened out.
I use this in other industries, also. Next time a telemarketer calls you or anything, try it. It works every time! 
Just make sure to change the story a little to tailor it to the situation or product they are offering!
Just make sure to change the story a little to tailor it to the situation or product they are offering!