IMEI number is assigned to the phone during manufacture and it's how carriers track your phone. Apparently Samsung uses it for some purposes also. Tinkering around with flashing/modifications after rooting can occasionally result in scrambled EFS partition which contains the IMEI. But if you bought the phone new and you're still getting your original phone service from your original carrier and it's working fine, then I really doubt that your IMEI has been changed.
If phone is reported stolen, the IMEI gets put on a blacklist. Anyone who buys a stolen phone may have trouble getting service.
I would push the button to contact customer support for more info. Big companies have been known to screw up on occasion ;-)