Ask about the goods you have ordered 2 months ago. You have got the company is confirmation letter that they will send you the good in 2 weeks. You have also got their invoice, but the details were not right(sum,amount). But you have not got the goods yet.
Explain the situation, bring out your problem and for further information. You write the letter, but you send a copy to the sales department. You add the copy of their invoice.