airlines - Not Allowed to Boad the Eithyad Airlines at Athens

I and my spouse both senior citizens, were returning from Athens-Greece to Mumbai via Abu Dhabi on **-**-** for my Etihad Airways flight # EY ** , PNR # QVEKEO, departure at **.**. I reached the Athens airport at **.** noon. I went to the Etihad Airways window for boarding pass and was shocked to know that I will not be allowed to board the flight as I didn't have Abu Dhabi visa. On explaining to the desk officer that I was only going to transit the airport for onward journey with a layover of *hours ** minutes. The desk officer sent me, to his superior, who told me that I had to show them the Abu Dhabi visa or else they will not allow me to board the aircraft. When I explained to them that I was only transiting the airport to catch the Goair flight, and as per transiting rules of the UAE government, I was not required to take a Visa, if I am only Transiting within * hours . Then the officer said that Etihad Airways doesn't partner with Goair and that without Visa they will not allow me. I requested the officer and me and my wife pleaded with them. But they only kept on repeating that Etihad Airways doesn't partner with Goair and we need a Visa. By that time my flight time for departure was over. I informed my travel agent but no help came from them too.
I had no choice but to go to Emirates Airlines sale's window as I could not find the Etihad Airways ticket window. I had to pay a heavy price for the careless attitude of the ground staff of Etihad Airways. As tickets were unavailable, I had to send my wife first as she wasn't feeling well due to stress with very expensive ticket and I was offered business class seat since no economy class seat was available, since, I couldn't afford the business class ticket. I had to catch the flight with Emirates Airlines on *nd November ** for which I had to spend ** hours at Athens and ** hours at Dubai over and above paying heavy cost for the ticket.
I am not able to understand the Agreements between airlines and the UAE government wherein the passengers of Goair airlines with a layover of just * hours were refused entry for not having a Visa. But the same passengers, if you travel with Etihad Airways or Emirates Airlines with a layover of over more than ** hours is allowed.
I have requested Etihad Airways in the feedback to consider my case sympathetically and refund my ticket cost of myself and my wife. but no response to date.

John K. +************