AITA for letting someone call me by a different name for MONTHS?

So this was about 10 years ago, but I still think about it often. Details changed to protect the innocent. At the time I was 21, young and working at a place with a LOT of foreigners. My name is long, and even though in English it is “simple” people always want to shorten it. I usually go by my full name … for example AnnaBelle but at times people just call me Anna, or Belle or this one person that I worked with often liked to call me A.B. All of the people that use these nickname usually have English as their first language. Well it got to the point I just let them because whatever, close enough I know they are talking to me… well then comes along this guy from China he meets me in a setting where that one annoying person calling me A.B. is there so this guy who is still desperately trying to learn English and get to know his new surroundings hears this and now things he is calling me Abby…. Well things get worse, someone tells him it is short for Annabelle but for some reason he hears Abigail, so this sweet guy starts to call me Abigail… I figure whatever maybe he can’t say Annabelle, he is only going to be working here for 6-9 months whatever, I let him call me Abigail, it’s cute.

Well… it is 6ish months later, we have worked together a LOT, I am off somewhere doing something and someone comes into the break room looking for me… for Annabelle. He says he doesn’t know who that is. They go oh you know that girl that is always here. He goes ‘do you mean Abigail?’ At this point his English has improved a lot. They are like ‘who?’ I come back to the break room and the person looking for me goes ‘oh there she is’ and this poor guy looks heartbroken, deceived and just all around shocked. And goes, ‘wait is your name not Abigail??’ There is so much hurt in his voice. I was like well, no… but it’s fine. He goes I thought people called you Abby… short for Abigail? Why do you not tell me your name wasn’t Abigail?? I try to tell him it didn’t matter, that I knew he was talking to me and I didn’t mind. He was so mad… so AITA for not correcting him, and letting him find out that wasn’t my name after 6+ months?