After Sarah Palin Asif Zardari a Victim of Prank Call

What a bunch of inept jokers have access to the nuclear code or button in Pakistan! A call ostensibly originating from the South Block, with the caller pretending to be FM Pranab Mukherjee threatened Asif Zardari with dire consequences.

There is a well laid out procedure for official calls to the PM and the President. How could this process be compromised?

How could a FM reach out directly to the President and not to his counter part FM?