Why Can't Standard Bank Stop Virus Emails?

I have been receiving Standard Bank "virus" emails for months and each time I receive one a screen pops up with a loud bell from my Avast Security, warning me. I have sent these to the Standard Bank security people - after phoning them - and they just say that I must delete them until they can fix it. However, today I received a further 3 of these Standard Bank "virus" emails and every day there are one or more. I have complained to Standard Bank, but I have received no response.