Ripped off by seller. How to complain about seller to shopify.

They make it next to impossible and do not respond. Very unprofessional. The shop I ordered from disappeared there are no links to contact or share. The website is gone days after ordered. Shopify and shop app should handle this. They need to vet their shops. They do not assist at all. It is useless to use them and even worse to order from a shop they list. Makes them complicit in my mind. They are aware of rampant fraud on their sites but do nothing.