Some schools dont give out A's for a grade that close because they have a limit to how many A's they can give out to a class. At my school there was a 25% limit of students who get an A for a particular course. But you can remark an exam, and sometimes they allow one or two students exceptions.
Ok this is what you should do: petition for a remark. My school let me check my exam and out of 3 times I petitioned, twice my mark increased.
The first time was a bloody addition error. The second time I actually argued that I deserved more marks, citing references. The third time the guy didnt give me an extra mark, even after I argued (citing references again). In fact he said I deserved a lower mark (luckily he was nice enough not to let the school know, because technically he could have reduced my mark lol).
Bottom line: with a 89.6% you have nothing to lose 🙂 GO remark your exam...