Strange Serial Number Problem

I bought an iphone 4 from VZW in september, 2011. All was fine until a few weeks ago when the "quiet vibrate" turned into a loud buzzing, which defeats the purpose of the vibrate.

Anyway, I brought to Apple Store. They listened to it and brought it in the back to look. After 10 minutes or so, they came out and started asking me if I had opened/altered the phone. I never have and told them so.

They proceeded to tell me that the serial number that is visible when you open the phone is different from the serial number in the "software". Apparently this indicates that the phone has been tampered with. I was shocked as I have never opened the phone (and wouldn't know what to do with it if I did). But they maintained that the warranty is void. How horrible being accused of something that I didn't do.

I looked up both serial numbers on Apple and they both appear to be valid and indicate that the warranty is in effect. However, apple will not do anything because the two do not match.

I have no explanation other than that was the way it was sold to me from Verizon. Did Verizon pull a fast one on me? Does anyone have any idea how I can get to the bottom of this and how and/or why this may have happened. I have not visited the Verizon store yet but would like to be more educated about this before I confront them. Apple would have replaced the phone if not for this serial number issue so I am relatively angry right now.

Thanks in advance for any help.

 

No Serial Number on receipt, but the serial number on the box matches the internal (system) serial number, not the number on the plate on the inside.

I will be persistent with Verizon but I wish I knew why would somebody replace the plate with the S/N on it? Would there be any motivation for a Verizon store employee to do this? What would be gained by selling me a phone like this?

Thanks