This email is in reference to the request having reference number _______ (mention number). I would like to inform you that I came to know that the services have been delayed due to ___________ (mention reason – miscommunication/mistake/technical error/any other).
Moreover, I am dissatisfied with your services as it took you ___ (days) to respond to my request. I hope that you will speed up the process and if you fail to do so, I have to take this matter further.
___________ (Contact Details)