New SIM in device, should I turn it to a trusted SIM? (Stolen phone)

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My device was stolen, IMEI is blocked by provider.  A "new SIM card on phone" message is showing in my account, but the new number doesn't appear. 

Should I click in the  "mark as found" link in order to get the new number? 

As a an strategy to locate it, do you recommend me to unblock the IMEI so the phone can log into the network?

After the new SIM was inserted, the communication with the phone was lost.  It had 41% battery, so I assume it's been turned off.

Thanks!

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Would your phone have activated the siren when the new sim was inserted? What was your phone set to do when a new sim was inserted (protection behaviour)?

Sirens and a "This phone has been lost or stolen" would prompt a thief to pull the battery straight away. 
Maybe if you mark it as 'found' and turn offf what the thief doesnt want to hear (sirens) and hope it gets a wifi signal allowing you to at least track it?

Pass any tracking info on to police! Dont be brave. It maybe in the hands of some very nasty people who may take offence to being tracked