Hi and welcome to the forum.
I would recommend SQL Express but Access will work.
Create a table that has an ID field, Department, Title, Number, Name.
Add some sample data, you can also import a spreadsheet if you have it.
Then create a new InfoPath form of a data base type and use the table as the source.
Then you can query and edit this list with the support form.
Then on your current form add a secondary connection to the table and use it for your drop downs.
This is very common where you create secondary forms for users to maintain their own data. Its a nice solution.