Paid Business Class, Bumped Down to Coach
 

My 75-year old mother, traveled on DL295, a 14-hour flight from ATL to NRT on Monday, 11/26. She was booked in business class and was issued a business class boarding pass at DCA, where she flew from. When she got to ATL and was boarding on the flight, the gate attendant 'switched' her boarding pass and she was bumped down from her business class seat in the 2nd level to a middle seat on coach 36B, without any notice. Has this ever happened to anyone?
Delta rep told me that they will refund the price adjustment for that portion of the flight and issue a $600 travel certificate for her, but that is not the point. There was no advanced notice on the change; I called two numbers for Delta Customer Care and none of them was able to explain why this incident happened in the first place. The fact that she already paid over USD 5,000 for the flights and already had an assigned seat in business class and they just took it away from her without further explanations is just wrong.

Hard telling not knowing. Possibly they had to switch aircraft because the original plane had a mechanical problem, and they were left with a smaller aircraft (fewer seats) to use. Airlines cannot pull planes out of their behind at a moment's notice. So if there were fewer seats, which would also include fewer first class seats, it's first come first served for those, and the rest sit in what's left.

At the minimum a bit of communication was required. Delta are just arrogant and totally lacking in any customer are.

You may want to request a cash refund.

Otherwise they'll give you a travel voucher which is only valid for one year. Further, in some cases, you can only redeem it at an airport!

I believe the traveler is getting both. I like to pay attention to detail. Here is a quote from the OP. The bold is mine for emphasis.