Please check my wrong grammar.

My answer

Hello. Ms. Crest, this is Binny from LG electronics.

I received your message saying that you ordered an MP3 player from/though/via/on our website. But important accessories were missing in the box. First, I am terribly sorry about this. These days there are a lot of orders, so one of our employees made a mistake. As soon as I received your message, I sent the accessories to you. Also to compensate you, I include a 50% discount coupon on/for your next purchase.

I hope you are happy with this message.

If you wish to speak more about this matter, please call me back at the same number.

Thank you.
player through website
on your next purchase