Delta - paid upgrade ignored; no refund.
 

Two weeks ago paid for an upgrade to comfort class. Checked in and was assigned normal economy. They didn't find a seat for me in the comfort class, and after communication refuse to offer a refund despite the fact their terms and conditions explicitly state that they have to. I have had multiple incidents with them. Please don't use this airline people, they are truly the most fraudulent airline I have ever had the displeasure to use.

Also
 

Forgot to mention they offered a small Delta credit towards my next purchase with them. Basically they are defrauding the customers in hopes of generating additional business. I will never use this airline again.

I would file a small claims court case. It will cost hem more than fighting it and cause them some inconvenience. Delta are horrendous... They will nly submit to force. They cannot charge for a service they did not provide.

Agree. If you paid for a service or product that they did not provide they are legally obligated to refund your money. You will probably have to escalate this issue to customer relations department. You should be able to find a contact on the Delta website.

Did you book with Delta online or with a travel agent?? If you booked directly with Delta, and paid for the Economy Comfort upgrade but did not board the flight in an EC seat, your credit card will automatically be refunded. There is no need to demand a refund, because again, it's automatic.

If you booked with a travel agent, then they are responsible for issuing your refund because they messed up and assigned you the wrong seat, and they were the ones who charged you for it so they have all the money.