Hi, Please refer to the following. You haven't provided the full details. Based on your narration, the draft below is made. You may edit it as per your requirement.
To
Dear Sir/Madam,
Ref: Contract of Agreement for deploying security dated_____
We have entered into a Contract of Agreement with your Security Agency for deploying security guards to guard our office premises. We had chosen your Agency with the hope that your Security Guards are highly trained and proficient to guard our premises. To our dismay, the Security Guard Mr._____ who was posted by you was found sleeping during duty hours. As you should be aware, Security Guards on duty should be very alert and should safeguard the office premises from trespassers or any third party entering the office premises with malicious intentions.
Now you are hereby required to replace the above security guard with a well-trained and efficient guard within____hours, failing which we will be constrained to cancel the contract dated_____
Acknowledge receipt
for______