Ebates Ebates Scammed me - not honoring their cash back on larger purchase Charlotte North Carolina

I have been buying stuff via ebates and only ebates site. I don't use any other site for cash back, since I used to use fatwallet.com, not they become ebates, I started using them since then. I always was getting cash back with no issues at all on any of the cash back I received, but most of them are in a few dollars to $10 maximum. However, I bought a cruise from groupon and went through ebates when they advertised 10% cash back on groupon after thanksgiving time. I never used any coupons as I know very well that will have issues in the cash back. Everything went well fine, I clicked ebates link for groupon and went there and bought. I can see the groupon showed up the items right away for $598 ($299 + $299). However, I didn't see anything on ebates. I waited for the second day, then I emailed them, they asked me to send all the details - waited for weeks, and now they denied this cash back sending the following details. Funny thing is other cash backs came through that are just a $1-$5 dollars same day/hour. 

I am really frustrated how these guys can cheat customers like this. I am thinking they falsely advertise and show 10-20% cash back so more people buy through them, but pay all the small amount and don't pay the larger ones, so they can pocket larger cash from the merchants and give cents to few dollars to customers so they can come back for more until they do a larger purchase and find out the real ebates scam. 

"Unfortunately, we are not able to add Cash Back to your account for the order from Groupon. When we looked into this order, we found that the order was attributed to another site that partners with this store. There are many ways this can happen. Here are a few examples:

· If you used a coupon or promo code that is not found on Ebates but found on another site, that site will be credited for that order. 
· If you visit any other site during your shopping trip (especially other sites that offer rewards, coupons, or discounts), that site will be credited for that order. 
· If you have a toolbar, plug-in, add-on, etc. installed on your browser (especially for other sites that offer rewards, coupons, or discounts), that site will be credited for that order. "

I now saw several complaints on these larger purchase scam from EBATES. Please beware.