Threads merged...
udayanveed, there are 2 ways to do this... The quick and painful... The slow and not 100% failproof.
The quick and painful: as N_LaRUE says, reset your phone and use a new email address for the Microsoft Account. You give up your Backups, your OneDrive, your App ownership, your saved SMS text messages... You give up everything and start from brand new user status.
The slow and not 100% failproof: Use a PC browser. Log onto your Microsoft Account. Add a new email address. Make it primary. Wait approximately 48 hours for the change to hit all Microsoft Servers. It will show on your phone as the new email address. It will show on the PC Browser. It will become your new email associated with the existing account. On your PC Browser, once satisfied the new address is in place, delete the old address. You keep your App ownership, you keep your OneDrive, you keep your Backups, you keep your saved SMS text messages... Potential problems: I personally lost the ability to verify password on my Skype profile to change info, another user reported a problem getting an Xbox Gamer Tag to transfer over. A follow up call to Microsoft Customer Care should help solve any minor glitch that appears after...