Del Taco review: customer satisfaction survey coupon

They offer a customer survey Invitation on receipt for one of the following on your next visit : (if you go online and complete a survey about your visit). You'll get your choice of one of the following: a free grilled chicken taco, or a free 1/2 lb bean and cheese burrito or $1 dollar off any purchase of $3.00 or more.
It has been my experience when I return with my completed receipt with validation code from the survey they totally don't want to give me my free earned item. (and yes I always make a cash purchase along with receipt so no I don't go in for just a free item). They are very rude about it too. If you don't wish to offer this program any longer just take it off of receipt. If a customer takes 5 mins out to complete your survey you should have the decency to honor the program without hassle.
I have been a loyal del taco customer for over 20 years and have never had a bad thing to say about Del Taco. But don't offer something and then make the customer feel unwelcome and or uncomfortable if they take advantage of your survey offer and you dont want to keep your end of the bargain.