May I Keep My SIM Card Instead Of The Replacement?

I just received my REPLACEMENT IMAGIO...

I've looked EVERYWHERE for the answer to this (especially in the instructions, on-line, FAQs, forums, etc)...

Nowhere does it say if I may switch my SIM card with the one that comes with the replacement.

The only thing it (the accompanying "PLEASE Stop and Read" card) DOES say is, "Clear all personal information from old phone" ... "...you MUST keep your original battery and battery cover  for use with your new phone."

It doesn't make ANY reference to the SIM card, which suggests that I am supposed to return MY SIM CARD with the old phone!

Why can't I just keep (and switch) the SIM cards?

My wife says I'm over thinking this, and it's likely OK to keep MY card....but,

I never like to assume.