The UPS guy just told you that there would be no charge to you from UPS. Dish picks up the shipping charge from UPS. Dish will charge you $15, no matter what the UPS charge might have been.
In my case, the $15 is a good deal. It would cost me about $22 to ship a receiver to Texas or Colorado, which I believe is where they go.
The Return Service (RS) or Authorized Return Service (ARS) is a special low priority service that UPS offers for returns.
I'll leave it for others to debate the morality of the charge.