Sir, please check this letter.
I have received acknowledgment of dispute letter from your side. In this letter you mention that “your dispute is under process which takes 30/45 days”
Sir, my question is that I received your bill amount Rs 3500/- due is date 30-DEC-2010. If am not paid this disputed amount Rs 3500/- till resolve this dispute. Do you charge me the late penalty or service charges?
acknowledgement is preferred in British English, acknowledgment in American English.