I want to cancel my free trial but all instructions on how to do so don't work. I tried the form as well but don't have an order number as I just downloaded it on my phone. How do I cancel without getting charged for the year??

I want to cancel my 7 day free trial but all instructions on how to do so don't appear to work. I tried the form but I downloaded the app so I don't have an order number. How can I cancel before the 7 days are up as I cant afford to be charged??