Ask about three specific things:
The insurance company (e.g., "Do you accept UnitedHealthcare?")
The specific plan type (e.g., "Do you accept individual/family plans?")
The plan's particular network (e.g., "Do you accept the Choice Plus network?")
Offices often only ask for the carrier name, but Thatch plans can have different network setups than employer group plans. Make sure they confirm all three details.