Tried to cancel subscription and was run around for hours between 2 representatives. I was not able to unsubscribe from their service and was being billed for it. I gave them my name, my email addresses, my phone number and offered to send pics of the credit card I used and got nowhere. I had to call card company and cancel the card and now have to wait 10 days for another card. All they had to do was remove me from their billing. Instead they now lost a customer for good and will be subject to bad reviews where applicable.
You can contact Shopify supporting for help. Read this article for more details, How To Get Shopify Support (Shopify Team, Forum, Third-party Partners)
Hope it helps!