I need to cancel the storage plan, I know longer have that phone

Realize the plan is not "on the phone" it is on your Apple ID which applies to anything you own by Apple. Are you sure you really want to downgrade now? If yes, read this link --> Downgrade or cancel your iCloud storage plan - Apple Support

At the bottom of the link I provided earlier it tells you what to do in that situation:

"If you don't have one of these devices, contact Apple Support to change your iCloud storage plan."

My first response really covered your situation completely. ;-)

If you don't have any other Apple devices or a PC, you will have to contact Apple Support -- Contact - Official Apple Support.