There's a SIM Lock and Network lock - both distinctively different!
- SIM Lock is to prevent phone from starting up unless a user's PIN is entered.
- Network Lock is what it is, tied to the carrier and requires the unlock code which can be bought for a fee.
By the sound of it, a confusion arose, when it asked for the SIM's PIN code that requires to be entered - which is NOT the Network Lock code! It is selected and decided by the user.
In short, SIM Lock has a maximum count of three times to enter the PIN code and if unsuccessful and the maximum retry count has reached, the PUK (Personal Unblocking Code) code needs to be entered!
The PUK code can be found on the original SIM Card plastic accompaniment as obtained by the original carrier. If this cannot be found, the only way is to take it back to the place of origin, where the SIM card was bought and explain to the Sales rep about it and may be charged!
(Now, they could easily be suspicious as in "handling a stolen handset"... get the original proof of purchase from the owner, documentation etc to back yourself up just-in-case!)
Ok, after clarifying with the OP, who kindly showed the screenshot in their edited question, the message is slightly ambiguous which lead to my not being 100% sure if that message when fed into Google' Translator is saying "PIN unlock the SIM network." Do not know if that is saying SIM unlock PIN or network lock hence the ambiguity.
But further investigation lead to this thread, specifically post #3 which does back-up the OP's statement, despite the thread discussing about Samsung, I would guess the same thing may apply to the Motorola handset:
I have also been told to remove CM9 and reinstall the stock ROM in
order for the unlock to work, but (1) I have no idea if this would
actually help, and (2) I have never changed a ROM before and, althouh
I used CM9 to create a nandroid backup, I have no idea how to
reinstall CM9 and then restore the backup.
That makes perfect sense, as the stock ROM would know how to handle the mechanism as its built into it specifically for the handset, so yes, a revert to the Stock ROM would be required which would obviously mean another OP's question to be posted separately or by per-chance, a quick google-fu to yield on how to revert back to original.