Do you know if they offer discount to any other services / trades / etc...?
I can get the same discount (also a bank worker). It's not bank specific. It's employer specific. The banks we work for have negotiated employee discounts with Vodaphone (and in the case of my bank Apple as well). So if your employer has negotiated an employee discount you can probably get the same. But if you are a plumber (for example) and are hoping for a discount based on your trade alone I don't think that'll happen.