Do you know when to say "a(ey)" and "a(aah)"?

[Sheng]

Example...

A call from Lucy...

Should we say (ey call from Lucy)? or (ah call from Lucy)? I believe there is a difference in pronouncing them, I just don't know exactly...

Help and thanks! :D

[Gray]

Please go through this post.

Hope this helps.
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First lesson - English, not english. I, not i. ~A student of English