They will NOT send you to collections over a $20.
By law there is a minimum charge collection agencies will accept.
I believe this amount is $250, but it could be as small as $100.

Ignore North Shore Collection Agency.
Simply send the envelope back with your request to cancell.
But my goodness, don't pay then expect a refund.

Their purpose is to scare you.
I have (for decades), subscribed to magazines and never paid.
I like to read one or two free issues - and why not.
Worst to get free - Oprah Magazine only sent me 1 free issue.

Keep a file of your endeavors.
And never, ever in your life pay by credit card.