Stupid Blockbuster #rant

So on Friday I rented "The Time Traveler's Wife" at blockbuster.  With my reciept I got a coupon for a free non-new release rental.  So today I go into blockbluster after work.   First, let me tell you that the lady working there tonight needs a lesson in Mickey D customer service.  The CUSTOMER IS ALWAYS RIGHT.  ugh!!! 
I get up to the register and I give her the movie with the coupon and we go through the checkout process, blah blah.  I notice that she is having a little trouble scanning the coupon, but I wait patiently.  Once she has it scanned, she tells me it has already been used.  I was responded, "No. That's impossible.  I just got it Friday and it's been sitting in my car ever since."  She starts to argue with me, "Ma'am, I'm sorry but the computer says it's been used so I can't help you."  Now I'm getting upset.  I know that I haven't used the coupon for gosh sakes!!!  So I ask her if the computer tells her what movie it was used on.  I'm curious what the stupid computer says.  She says that it was used on the 12th.  I say in a snotty tone, (I'm feeling smart, yes), "um that's today, you scanned the coupon a bunch of times, probably."  I've upset her, oh well.  She goes, "oh i was jumping ahead of myself, i scanned it and now it says its used so i was telling you that.  I didn't scan it too many times."  Whatever lady just give me my free non-new release movie. 
Now let's talk about how this would have been handled at my store.  First of all, if you don't want to deal with a customer, give them whatever they want.  I was renting sweeney todd.  This movie is old.  Just give it to me for free.  Ok so you have the time to deal with customer.  Never argue with the customer.  You need to investigate the situation completly and if the situation requires it, explain to the customer why it is they are wrong in a very polite manner.  If the customer refuses to be rational, then again you resort to giving the customer whatever they want.  This is how you keep customers coming back. 
What I would like to focus on is that the lady who was helping me did not investigate the situation completly.  As was obvious when she said "oh it was used on the 12th".  Um that's TODAY you IDIOT!!  And the other thing, how in the heck could I have a used coupon when you keep them after you scan them!! Does that make any sense!!
Ugh. anyways, this has made me feel better about the situation.  So I will continue to watch the rest of this movie which I rented for FREE with my UNUSED coupon. 
Lastly,
Dear stupid Blockbuster lady,
COME WORK AT MCDONALDS!!! THEN YOU WILL MEET ANNOYING CUSTOMERS!!!
kthanksbye.