To cancel a MC311 request for service, simply call 311 (or 240-777-0311 from outside the County) and speak with a Customer Service Representative during the office hours of 7:00 AM to 7:00 PM, Monday through Friday. Please have the number of the request you would like to cancel. If you do not have the service request number, you may provide any relevant details such as name, address, or other information.