My first name can have a couple of variants, my surname any number. I'm aware of this and usually take the time to spell out particularly my last name. Like you, it irritates me when other people can't be bothered to follow the guidance I give. If they can't find me, it's usually because of their error and not mine.

I think a lot of times people just don't care. Especially in places like hospitals, they deal with a million people every day and I'm sure that patients can easily become just another body they need to treat. Don't get me wrong, I'm not defending them, but I can see why they're less than careful about people's names. 

I don't know how many times people have gotten my name wrong. Even when I'm spelling it out for them, they can't seem to wrap their minds around the letters I'm saying.

I was trying to get into a building once and the security guy had to look up my name on the visitors list. I spelled my last name for him, gave him my ID with my name on it, and I watched over the counter as he typed my last name wrong. I spoke up and corrected him, and he re-typed it... wrong again. It took him 3 tries to get it right... my last name has 3 letters in it, not that difficult, folks.

My husband works for a hugee comapny, hundreds of thousand employees worldwide. At one time there was a sales man with the same first name and last name spelled with an e not an "i". They frequently got each other's email. One Saturday my husband had been called in to cover an absent employees shift. A woman making a left turn on a green arrow failed to yield right of way to a pedestrian in the crosswalk, my son. The responding officer took my driver's license and called the main number where my husband works to have security tell him that his son was being taken to the local children's hospital. The receptionist entered the name with the e, left a message for the other guy that his son was hit by a car. Thankfully that guy only had daughters. 

When th message finally did get to my husband, it was his daughter to the local hospital, which confused him since she lived 120 miles away. Simple details, like an I, e, or a whole name are important.

I have had this type of experience too in my life. Even till now my first name will be written with wrong spelling by everyone. I will request them to put on correct spelling everytime. Some times they don't listen and some times they don't care. Sounds funny but we are the ones we feel offered or embarrassed because of someone else's perception and understanding.

I double barrelled (without a hyphen) but Cris didn't. I kept mine pretty much solely for teaching purposes. Because there's no hyphen, it becomes a middle name, and my last name is just four letters long - and the variants you get are amazing!

I feel for you sweetie. Names are important, regardless of the size of the institution someone works in, and it's not hard to spend ten extra seconds getting it right.