Identify the customers that have been booked but are still appearing, bring up the customer.
Click on the service job and look for 'Original Job Details' section there is a option called 'type.' Click on that and make sure its set to the correct type e.g. 'Boiler Service'. When you're entering the job, make sure you select the 'type of job' option and the system will then know that it is a boiler service.