I once worked at an organisation that rolled out logon ids that were First Initial, Last Initial, Payroll Number (eg lh891234). Except for our small department who had started before this roll-out. Whenever we contacted the HelpDesk we had to go through the rigmarol of "your ID is your payroll number..." No it isn't! "Yes it is, your ID is your payroll number..." No! Listen to me!
It was a struggle, but we eventually forced them to migrate us to the "standard" logon ID scheme.