[Grammar] Should I put an article?

[brianna]

Hi, I'm glad that I found this site and ask English teacher if my sentence is grammatically correct.
I'm writing a introduction part of a online survey.
To encourage customers' feedback, I want to introduce myself and want to tell them how I got their names.
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My name is Gloria Yang, ----- product manager at XXX company

Here at XXXX, we are currently going through a process to evaluate XXXXX product and I was given your name by sales reps as a professional whose opinions and concerns would be of great value to this survey.
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Should I say "a" product manager or it is okay to say "product manager" without an article.

Your answer will be very appreciated.

[hanky]

I suppose that A or the is needed. (BTW I will replace "at" by "of")
Not a teacher