Keep your mobile number and change your operator so simple.
Most of us wanted to change the number because of the operator but could not change it because we would have shared their mobile numbers with many contacts and would not like to leave the number. At last MNP is happening from January 20th 2010. And it should happen in 4 days as the law enforces.
change your operator in six simple steps
You are done with your operator changing :)
Another thing to keep in mind about MNP is that even though a subscriber is free to keep switching service providers as many times as he/she wishes to; they would have to stay for 3months with an operator.