vibe during call waiting problem

Hey, tried searching, but couldn't fins any info on this (maybe I just suck at searching )

When I am talking to someone on the phone,and the 2nd call comes in, my phone starts to vibe. Problem is that the person I am talking to can hear vibration as well until I put him on hold and answer the 2nd call that is coming in.

Any ideas why this is and how to possibly fix it? Can it be changed so that some alert is played when the 2nd call comes in and no vibration occurs (would other person hear this alert?)

Thanks for your help.