I did that. There were no options, just a dialogue saying they had refunded me a couple dollars for a price mismatch. But no button to report an issue on the app or web, no chat, no email or phone number. Just a Contact Us form that I filled out and submitted with all the information nearly a month ago, and no one from GrubHub has reached out. I finally just did a chargeback a couple days ago.
Block those communities or ask the admins of your instance to defederate if there’s not much redeeming content from the offending instance(s).