How to cancel the Basic package trial?

Hello. I recently created a dropbox login and went with a basic free package. It required me to add a credit card and advised that I would be charged monthly if I didn’t cancel the free package by a specific date. I have made several attempts to locate where I can cancel the free package on my mobile as that is how I signed up, but there is no way for me to be able to do so. There’s also no other option for customer service support through dropbox