After your unlocking Or Jailbreak your iphone on 3.1.2 Firmware might get the problem for your iphone can not cennected to Wi-Fi.

NOTE: Your iPhone 3G/3GS should be fully unlocked by using blackra1n RC3 & blacksn0w.  for complete instructions on jailbreaking your iPhone with blackra1n RC3 and instructions on blacksn0w.

FIX-1: Reset Network Settings of your iPhone

As per GeoHot, he received enormous WiFi/Hotspot connection issues/queries from users who upgraded their iPhone using blacksn0w/blackra1n RC3. The resolution he recommended was to reset your network settings of your iPhone. Follow following simple steps to reset your iPhone's network settings.

Step-1: On your iPhone, go to Settings –> General –> Reset –> Reset Network Settings. You will see a "Reset Network Settings" button as shown below.

Step-2: That's it. Just touch this button and give a power cycle to your iPhone, i-e turn OFF and then turn ON your iPhone.

Please keep in mind that this isn't a permanent solution to this WiFi bug, it may arise again and you may have to perform same steps to reset settings again.

You would have noticed that Push Notifications are not working on jailbroken and hacktivated iPhone 2G/3G/3GS on firmware 3.1.2. This tutorial will help you to enable Push Notification on your iPhone on firmware 3.1.2, all you need is an unlocked or jailbreaked iPhone.  your iPhone and follow step-by-step procedure given below.

Steps to Enable Push Notifications On iPhone 2G/3G/3GS on firmware 3.1.2

We had try this method working :

Start Here : go to cydia - source - add source - add " fishbone.ge "  to section P install the Push notification Fix after the phone will restart your Youtube should working now, if still not working try the next steps bellow,

Step-1: There shouldn't be any "push-capable apps" installed on your iPhone, you need to uninstall all Push-capable apps from your iPhone, if there are any.
Step-2:

• Start "Cydia" on your iPhone.
• Touch on "Manage" tab on the bottom.
• Now touch on "Sources" as seen in the screenshot Left

Touch on "Edit" and then on "Add". You will be prompted to enter a url source as seen in the screenshot below. Type "http://cydia.iphoneil.net" and touch on "Add Source"

Cydia will now automatically update your sources with a series of automated steps.

Step-3: After installation, search for "Push Fix" application in Cydia and install it. This application will fix Push Notifications on your jailbreaked and unlocked iPhone.

Step-4: After installation of "Push Fix" application, you will need to Restart your iPhone before you install any "push-capable apps" your iPhone.

Configuring Apple iPhone for the Bell Mobility HSPA network, For apple iphone APN Setting for Bell

The following instructions can be used to manually configure the
settings on an unlocked Apple iPhone 3G for MMS and Browser on the Bell
Mobility HSPA network.

1. Follow the instructions in the user manual to install your Bell SIM card into the phone.
2. Turn on the phone.
3. On the Home screen, tap the Settings icon.
4. Tap General.
5. Tap Network.
6. Tap Cellular Data Network.
7. In the Cellular Data box, tap APN and enter: pda2.bell.ca Leave the Username and Password blank.
8. Scroll down, and in the MMS box: - Tap APN and enter: pda2.bell.ca - Leave the Username and Password blank. - Tap MMSC and enter: http://mms.bell.ca/mms/wapenc - Tap MMS Proxy and enter: web.wireless.bell.ca:80 - Leave the MMS Max Message Size and MMS UA Prof URL blank.
9. Press the Home button to return to the Home screen.

Please note that you will have to re-enter the above settings
anytime you insert a different SIM card or if you reset the settings.

In case your iPhone is yet to be activated, you can try dialing a secret number – *3001#12345#*

Once you make the call, you can tap on version to reveal the version number. If you dial the above number on normal iPhone, you’ll be brought to a field test screen. Note that the secret code may not work for all iPhone firmware versions.

make Sure your have any SIM card in the iphone

Hacktivation Patch For Different SIM Detected Error On iPhone After Activation

With Phonebook SIM or Different SIM Card.

If you were able to jailbreak iPhone, activate without original SIM, and even finally unlock iPhone. But when you finally replaced the phonebook SIM with the unofficial SIM, you are surprised to see the ‘Different SIM detected’ message, asking you to connect to iTunes.

Well the reason for this is that Apple has blocked phonebook SIMs. So here is an easy to use hacktivation patch for your iPhone to get rid of the ‘Different SIM detected’ error, given by Sherif Hashim the same guy who gave us the phonebook SIM iPhone activation trick.

hose of you who already have the pushfix repo in Cydia can go ahead to step 5. This is the from the same author who also gave us the fix for push notifications.

1. When the error ‘Different SIM detected’ is displayed, replace your unofficial SIM with the phonebook SIM. This will get you out of the emergency mode.

2. Start Cydia from your iPhone springboard.

3. Touch on ‘Manage’, then ‘Sources’.

4. Touch on ‘Edit’ and then ‘Add’. Add ‘http://cydia.pushfix.info’ as a source and hit ‘Add Source’. Let Cydia update it’s sources.

5. Now that the repo is added, go back to Cydia and search for ‘Hacktivation Patch’.

6. Install the app.

That’s it. You can now insert your unofficial carrier SIM and will no longer face the ‘Different SIM detected’ error.