I dont think most of the MTNL tech staff would be knowing as he had to tell someone in the control room on phone and guide him how to remove the existing mac address.
So, next time it may need you to go to the exchange and get it done. I am not sure if this is a good thing or a bad thing, but i thought you guys may find this info useful sometime.
Thanks for the heads up. In general, it is best to keep the old router around before you put a new one in. Also, spoofing the Mac address is easily done. The exchange can go to hell.
Cheers,
Amol Hatwar