The SIM card in a i730 slides out of the side of the phone. Remove the battery and simply slide the card to the right toward the push to talk button.
Once removed you will see a diagram that shows how to insert the new one. You need to insert it with the angled edge down to the left.
If it is a new SIM card you will need a SIM copier to copy the contacts from one card to another (if you want to)
You will also need to activate the new card before using it. Go to a Nextel store for this or try customer service.

With the Motorola i730 there is either 2 options on it,
it may be a Push and it pops up to insert the sim.
the area for the SIM card is in the middle of the phone, after removing the Battery, It should be either like you said, a metal plate, or a metal holder that extends. Let me know how it goes,
Thanks
Justin
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