Very vague question bud.
1. I wouldn't do DNA because you'll have a pissed off driver who gets that call saying "why didn't you deliver so and so customers food". Plus hurting the drivers is wrong
2. It's not as simple as saying "food not get my door please send help". Depends on account history, location (US, Canada, UK, Etc), what you bought and from where, etc.
Plus you probably aren't going to have many food reunders commenting on here and giving their methods away lol
If you want success, use a reputable food refunder. I heard Throbanksy was pretty good