To,
The Manager,
__________ (Post Office’s Address),
__________ (Post Office’s Details)
Date: __/__/____ (Date)
Subject: Complaint about a Delayed Package
Respected Sir/Madam,
I am writing this letter to bring to your attention an issue I have encountered with the delivery of a package. My name is ____________ (Your Name), and the tracking ID/ Courier ID/ package number associated with this matter is _________ (mention the tracking ID/ courier ID/ package number).
The package was initially scheduled for delivery on __/__/____ (Date), but unfortunately, it has not reached me as expected. It has now been _______ (number of days) days since the anticipated delivery date. I am concerned about the delay and kindly request your prompt attention to ensure the immediate delivery of the package.
I appreciate your understanding and cooperation in resolving this matter promptly. For any further inquiries, please do not hesitate to contact me at ___________ (mention contact details).
Yours truly,
___________ (Your Name),
___________ (Your Contact Details)
lettersdadmin 
Rahul Sharma