To unlock a phone for o2 do you need an o2 sim card in it?

SOURCE: Unlocking network

This is a BB5 handset, these handsets can almost always only be unlocked by the network provider. After 3 attempts of failing to enter the correct unlocking code will result in having to get it unlocked using specialist unlocking software and cable.

SOURCE: unlock a nokia 2630

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This is not supported by your phone manufacturer. Use this at your own risk.
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Here is a tool you can use, it works for most providers, including the two you have mentioned here: O2 and T-Mobile.

http://www.unlockme.co.uk/dct4free.html

SOURCE: unlock nokia 2630

go to unlock.nokiafree.org 

SOURCE: I need Nokia 6270 Restriction unlock code

Hi

I need Nokia 6270 Restriction unlock code.Can you help me?

SOURCE: nokia e65 will not accept any sim card after i unlocked the phone

I would try the unlock again, it sounds like the unlock was unsuccessful otherwise it would have allowed you to use the other sim cards.