They cancel the card and eating up my rewards for no reason - American Express Costco Credit Card

I opened Amex Costco Credit Card when I became a member of Costco. My credit score was 740+ and they readily approve the card with a $3000+ credit limit. My average balances were around 400-450 and paid in full all on time for each billing statement for 6 months. One day I swiped my card at a restaurant and card was declined.

I paid with another card and called American Express on reaching home and they told your card was cancelled 5 days back. On asking the reason they stated, change in your credit score since you applied for a card and too many credit enquiries in last 2 years as per the report by Experian. Next day I subscribed for Experian Credit report and my score was 730+, there was no missed payment on any cards and there were usual 3 enquiries, one by Amex when they opened my credit card and two other by rental screening companies as we moved to another state and changed our apartment after 6 months lease was over in one of the apartment. I called Amex that though I don't need you credit as my total credit line is above 8k on 3 different cards but still want to know what is the specific reason and I use this Card at many occasions including purchase at Costco. They told we can not do anything and you can send a fax of your credit report. Done, did that, no response from them. I received my final statement after 2 weeks and they gave me travel rewards for one hotel booking and there were three flight tickets booked for $1850 for my family and no rewards for those, when I called them, they told as your card is cancelled we are not giving those rewards, wt* my card was in good standing at the time of booking and I paid all the balances on time, this is your own decision to cancel and then you want to eat my cash reward also. I could have used my other cards and received 2% reward.

When I searched on internet about this practice by Amex, I came to know it's common for them to eat the rewards. I really feel they are the biggest cheater in the Credit Card Industry and I am open if any one wants to initiate a formal complaint about them. I don't know what to do, it's not a question of $ 50 or so cash back, it's a question if honesty and malpractice cheating with the customers. Now if I don’t pay my balance they can charge my interest or can report to credit bureau, I wish if customer also have something like to do a complaint to a credit bureau and to any other court for companies like these. I am never going to go for this company and wish they vanish from the business soon.