Re: Complain letter
The address and salutation are fine. I find it odd that a machine has a date but I assume this is some technical information that they need. I would write the body of the letter like this:
This is to notify you that the above-mentioned machine is not functioning correctly. When we press the "0" (zero) button once, the machine registers "00" (double zero). This is causing a huge problem for us when printing reports.
Please arrange for a technician to attend and repair this machine as soon as possible.
Yours ... etc
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.