3.1.2 needs to upgrade

[steelers760]

I currently have an unlocked iphone 3Gs 16gb running on 3.1.2 which I jailbroke with blackra1n, and i need to upgrade my phone at least to 3.1.3 because I have the NFL sunday ticket and the app needs 3.1.3 at least to run. Is there a way to update my phone to at least 3.1.3 without losing my unlock because I am on T-mobile network. Is there a way to do this without using a ATT sim card since I do not know anybody with an ATT sim card.

[iYeow]

Is your jailbreak at 3.1.2 untethered? It simply means that if you do not need the aid of pc to power up after powering down.

[steelers760]

my phone is tethered. I forgot to mention that

[iYeow]

On your front page of Cydia, the green letters, tell me what shsh is shown there.

[steelers760]

my SHSH blobs are 3.1.3, 4.0, 4.0.1

[iYeow]

Alright , I suggest you restore to 4.0 or 4.0.1, no difference between the two.
Are you on a pc or mac? I am only familiar with pc.

[steelers760]

I am on PC. If i upgrade to 4.0 will I lose my unlock?

[iYeow]

No, you will get untethered jailbreak and be able to unlock. Unfortunately you will need a valid sim to activate. I will proceed with guides after your reply.

Before you start, sync all your contacts and photos .
Click Start > type Notepad > run as Admin > and browse to :
Cwindows\system32\Drivers\ect\hosts and add this line to the very bottom
74.208.10.249 gs.apple.com
everything else just temporary comment out with this # , save it and reboot.
Now Download the 4.0 or 4.0.1 ipsw from here :
iClarified - iPhone - Where To Download iPhone Firmware Files From
Put your iphone into Recovery mode : Turn off the iphone, while holding the Home Button, plug your Iphone into the pc until Itunes Cable logo appears.
Do the Shift + Restore to 4.0 or 4.0.1 ipsw
Let it restore and when finished, you arrived at Emergency Screen.
Put your Valid sim card,it can be an unused sim , not activated will do the job or borrow from your friends if you don't have one.
Setup as a New Iphone to avoid conflicts.
Once Activated on Springboard , open Safari and go to jailbreakme.com
Under Jailbreakme 2.0, click that and it will bring you to Slide to Jailbreak.
Slide it and make sure the auto lock is set to off for this jailbreak to finish.
Once done, update Cydia and unlock again with Ultrasn0w.

Edit : If you want to backup all your Cydia stuffs, use Pkgbackup from Rocks or Cydia. The price is $4.99 but it is worth it.