YANBU, it IS annoying. And yes, I can't imagine WHY someone decides to call you a different name to the one you told them. I was recently introduced to 2 women called Angela and Olivia; I have no intention of calling them Angie and Livvy. I would expect a short shrift from them if I did!
Used to happen with my daughter too when she was a child. Her name is Chloe, and some people called her CHLO.
It sounds utterly vile. CHLO. Really pissed me off it did. The name only has 2 syllables - it's not that much effort! 
Now she is older (20's,) it doesn't happen.
As a few people have said on here, I have known a few people complain that their name is lengthened. Some people are called 'Katie' or ' Lucy,' and this is on their birth certificate, and yet people say Katherine or Lucille. Very annoying.
What annoys me more is when people get my name WRONG. 
I have a fairly big extended family of siblings, cousins, aunts, and uncles, and when I was much younger, I never saw a week go by without some family acquaintance or neighbour or SOMEone calling by another sibling or cousin's name. Really pissed me off.
I also used to know a woman who knew exactly what my name was, and my husband's too, and yet she sometimes pretended to 'forget' like we weren't important enough to her to get our names correct. 
Needless to say, we ghosted her pretty sharpish.