The post you have is not very clear on the issue. Are you saying that your company has short codes on the company phone system that automatically dials the relevant mobile number?

The N900 picks up the transmitted caller id given by the network. If the company aren't transmitting their number or the carrier isn't forwarding that to the phone then this isn't the N900 at fault, no phone would be able to do this.

Can you clarify your situation please?