This is wrong ! Plain and simple. $6.42 is probably more than the cost of the coffee.
Here are somethings you as a consumer can do to help,
1. If possible visit the restaurant personally, and order to go
2. Find the restaurant's phone number on their website / Facebook / Instagram / twitter page.
3. Leave a tip
I've found that yelp / google phone numbers can be in-accurate or lead to a proxy number.