You can contact Grubhub through the order itself in the Grubhub for Drivers app.
Follow the below prompts to open a chat window:
- At the restaurant, tap There is a problem on the order details page and then click Order is not ready to activate chat
- When trying to make a delivery to the diner, tap There is a problem and choose Diner is not home to activate chat
- If you need to contact the dispatcher prior to the order start time, go to your task list, open the order in quest, and tap There is a problem