I did the same today after trying to make Cakewalk support Understand. I asked what the best way was to cancel my monthly payments and make a one time payment or full licence for Sonar. The reply I got back after a week was that there was no way to credit my 2 months and pay the balance of a years membership.
In the meantime surfing around I found a page where I can cancel my monthly order yay..
So I just went and placed an order for the one time payment Sonar Platinum whoops. Got taken to a PayPal site in another language. Back I go and his time all done in English and OK
Where am I now. I've let Cakewalk know I've got an order I don't want and I'm going to cancel my monthly repayment as soon as I get a serial number for my new and paid for Sonar Platinum licence. It's already been a few hours. I hope it doesn't take too long to get the serials so I can just done what needs doing.