A gateman keeps the outer entrances into the Banking Hall. His Responsibilities are every action that enables Banking activities possible within the Banking Hall which it's core activity is PREVENTING INCURSION OF INTRUDERS with ILL intents from gaining access to the bank.

A banker is him/her who serves renders financier services of the said bank to Customers which could be directly ( cashier's) or indirectly (personnel staff) to mention , but few examples.

Please note that both the Gateman and the Banker renders equally important service to their Employer!! Both could be equally educates as well. Just division of Labor within an Organization.