Dear Sir or Madam,

I am writing this letter to complain about a laptop that I purchased from your shop last month. It is a MacBook Pro and the invoice number is INV1234. 

As for the issue with the laptop, its display and keyboard have gone haywire after using only for a month. There are thin black lines on the screen and I tried to resolve it by running a software update. However, it acted the same even after installing the software. The keys A, J, C and K do not function properly and are posing as a roadblock for my work. 

I am a software developer and my work involves using the laptop extensively to develop applications, attend meetings and review my team’s work. As a consequence of the aforementioned problems, I am unable to carry out my responsibilities. 

I request you to replace the laptop as it has a warranty period of one year. Please send in a technician to check the product and deliver a new laptop as soon as possible.

I look forward to your reply.

Yours faithfully,

James Gunn