The sounds may be easy to pronounce. The people may just not be devoting the attention to remember it. They've been told it's "Isabeya," say, but they just keep forgetting it's not "Isabella."

I would treat this as similar to forgetting someone's name. Yes, plenty of people have a "terrible memory for names," but at the end of the day it's a matter of respect. If you really care -- if it's someone who's becoming a friend, if it's someone you ought to know for your job, if it's someone who's been introduced to you five times -- it's on you to remember the name, unless you have a genuine neurological condition.

The most basic form of respect is to get someone's name right. Or at least make the effort.