What are the speakers mainly talking about?

W: Can you help me for a minute?
M: Sure. What can I do for you?
W:(1)I’m trying to write a letter to one of our clients, but I just don’t know exactly what to say. I don’t even know how to get started. I know I should write "Dear Mr. , Mrs. , or Ms. " , but the problem is I don’t know the name of the person.
M: You can just put " Dear Sir or Madam" , or you can write " To whom it may concern".
W:(2)OK. So I first thank them for their business. I can say something like "we are very grateful for your support". How is that?
M: Good! But also tell them the reason for your writing, and give them more references.
W: Like "Regarding our new product line, we would like to announce a special price discount. "
M: Right. Do you need them to respond?
W: Yes, the letter would have a survey inside, and they should complete it and return to our office. How should I write that?
M: You can tell them "Please find the enclosed customer service survey" , also, you can say, "Attached a customer survey. " If you need resource right away, you can tell them the urgency by saying " Please return the survey without delay. " Maybe it is more polite with this—" as early as convenient".
W: Great! And what do you think I should close it with?
M: Since you don’t know them that well personally, probably the best way would be "Yours" or "Yours sincerely".(3)You can also say "Best regards". But I don’t think it would be proper because you don’t have the name. And obviously, you should have them.
W: OK. Thanks a lot for your help!