How to unlock mobile phone

Why unlock a phone?
Unlocking is the opening of a phone to allow it to use any network, and removing the restriction that the original network placed on there. Several reasons for doing this are: Cheaper on another network, the phone is cheaper on a network but you don't want to use that network, the phone is moving country (be aware, some countries including Spain outlaw the unlocking of phones) or a person just want different networks open on their phone.

There are a lot of phones on the market today that cannot be unlocked yet, and there are a lot of people scamming and making money from this. I hope to mainly cover the basics in this thread, if you have any questions that aren't covered, please PM me and I'll get back to you as soon as I can.

Also, please remember most phones cannot be unlocked for free. A lot of time, dedication and work go into the development of software to give you the freedom to escape your current network, so don't be surprised if the only answer you get is, "See a professional to get this model unlocked".

Nokia
There are three major groups for Nokia's as far as unlocking is concerned.
DCT3
All DCT3 phones can be unlocked remotely provided that the codes haven't previously attempted. If they have, you'll need professional tools to get them unlocked, I recommend paying a specialist to do it (much cheaper then buying the kit) if this is the case.
DCT4
All DCT4 phones can be unlocked remotely provided that the codes haven't been previously attempted. If they have, you'll need professional tools to get them unlocked, I recommend paying a specialist to do it (much cheaper then buying the kit) if this is the case.
BB5
Most BB5 phones have been cracked or are close to being cracked. There are no BB5 phones that can be done by code, and if you ask in the forums (http://www.zedge.net/forum), your thread will be linked to this one and locked, or deleted. BB5 phones include:

- Nokia 3250 5200 5300 5500 5700
- Nokia 6125 6126 6131 6136 6233 6234 6270 6280 6288 6500 Classic 6500 Slide 6630 6680 6681 6682
- Nokia 7370 7373 7390
- Nokia E50 E60 E61 E62 E65 E70
- Nokia N70 N71 N72 N73 N80 N90 N91 N92 N93 N95

List gathered from various sources, if your model isn't listed here and is fairly new, it's safe to assume it is BB5. If you are still unsure, please post and ask, but make it clear you have looked at this list and I'll update it! The current process is risky, involved, usually expensive and very difficult for these models, still best to try through your operator. Please note well that the unlock not only depend on the model number, but the version number too. To get these phones unlocked, visit a local unlocking centre or contact the guys at nokiafix.com for more details.

Sony Ericsson
Most SE phones can be unlocked, however I don't know of any code generators, so they must be done via cable/software. I highly recommend taking these to professionals that insure against damage, as even I get these wrong sometimes.
Major groups in Sony Ericsson are:
DB2010 - CID16
DB2010 - CID29
DB2010 - CID36
DB2010 - CID49

DB2020
CID49 can be done without issues
CID51 may need to be re-flashed, hence data loss
CID52 can be problematic, but usually fine
CID53 same as CID52

Motorola
All motorola's that I know of can be done, however some are more complex then others. Motorola codes are not generated using the IMEI, but they can be obtained using it. I personally have access to a code record system for 2G handsets, however I cannot generate them, and this is a paid service. Otherwise, feel free to post for more information on unlocking yours. As a general rule though, codes are not free but depending on your model there may be unlocking software available (again, not necessily free).

Samsung
Some Samsung's can be unlocked using generic codes, there is a thread in this forum with all the codes found up to date. However, these only seem to work on older models, and can kill phones if not used properly. Otherwise, all other models can only be done by professionals.