Use of A and AN

How many of you today are still confused of using "A" and "AN" in a sentence?

I'd still remembered, I was on a jeepney way back home when i heard this two ladies and they're arguing on on how to use "A" and "AN" in a sentence,the feeling when you heard them arguing and you knew they are X.
As i've noticed,they're both working in a call center company as what i read on their id's position is "customer service representative" and the company name is "----", closed to the company where i worked before, but  imagined,how could they get the job but still didn't know how to used A and AN.These were probably taught at school.I remember i've learned it from school when i was in grade school, i think.
But whatever it is! As what i've  learned from school "an" is used before any word beginning with a vowel, and "a" is used before any word beginning with a consonant.

I really couldn't imagine any blog post today so I was very glad to meet them!:-) 
It's nice to finally make some sense out of it all.

Have a good day!