These 'clerks' go by many names, and the name they go by is how you buy the ticket to Hell that they offer. There's several hundreds that go by the same names, since they have a lot of territory with thousands of people to reach. Their name is on the ticket you buy from them. When they get promoted to a master demon status, Satan, their boss, gives them a new name. Don't worry, your 'clerks' will still go with you on your trip.
Clerks always work in teams.
Where there is one, there are many. They do not travel alone. Now, you can obtain several tickets along with your regular ticket if you like. The 'clerks' would be more than happy to promote your position for you. It costs a little more, but they will make it EASY for you.