When i change new sim mobile askes me phone code.

If it is a used phone and it was never wiped. Then the old security code is active. Changing the sim does not change the security code of the device. If it is asking for a sim security code, then the sim card is locked and you must have the code or the sim is just a piece of plastic. Did the service provider put a code on the sim and forgot to tell you.?..Take the sim back and ask for another without the security code on it. Sims can be coded so that if they are stolen they cannot be used in another device.

PUK code comes with your phone sim card when you bought it.Try locating where the whole box or package of your phone. Some sims comes with a manual and usually the puk code are written in there..Others comes like a regular size card and you have to detach the sim from there..in this card thee should be two Puk code that is written..
Hope that this info has help you in anyway..have a nice day..

might somebody change your code,thats why everytime you change a sim,it will ask for a security code
le

Try this :

* turn off your mobile
* remove battery for an hour
* put it back and turn it on
* enter the desire code of yours

if doesn't work? needs to go to the nearest mobile service shop and ask assitance for code retrieval.

this code can not be calculate or can't be request because this kind of mobile has a new security module..

hope it helps...

put the first sim on your mobile...but before that follow this steps

* turn off you mobile
* remove battery for an hour
* put it back the turn it on again

* insert the 1st sim that you have made a securitycode,try to change it if its possible
* if success,try to insert the 2nd sim the enter you previous code

if ask for a "new security code" enter 12345 or your previous code

HI If you are asking for pin contact your service provider ,
he will give you a default pin .
If you try pin more than few predefined no of times your phone will ask PUK
code which can also be given only by your service provider which is specific for each and
every mobile number . Do not try PUK(new pin code) code many times or else your sim will be
blocked and you will need a new sim.
Contact your sim customer care department over phone. Its free of cost to get the pin or puk no.
Go to the nearest service outlet of your service provider they can also help you.
There is no other go than the above procedure only your service provider can give it nobody else
in this world nor any software.

Hope this helpout......

When you place a new or a existing SIM card from another phone provider into your mobile phone and it asks for a Security code then :-
This phone is locked to the original mobile phone provider. You need to contact this mobile provider to ask for the unlock code (security code) for this phone. You need to provide proof of ownership etc and the phone's unique IMEI number which is located inside the phone under the battery. They use this number to generate the unlock code for your phone.
They should provide you with instructions on how to enter this code into the phone.
Once you unlock the phone, then you can insert a new SIM card in this phone or sign up with another phone provider using this phone.
You could ring the phone provider and ask for the unlock security code because you are going overseas and wish to use your phone with a prepaid SIM card from another country. This maybe a free service.
The other way to get your phone unlock is to use a phone unlocking company on the Internet, they usually charge a couple of Dollars for their services. Use Google and search for "Security unlocking code” companies in your area.
You can also try this WEB site :-
http://www.mobileunlockguide.com/mobile-phone/

When you place a new or a existing SIM card from another phone provider into your mobile phone and it asks for a Security code then :-
This phone is locked to the original mobile phone provider. You need to contact this mobile provider to ask for the unlock code (security code) for this phone. You need to provide proof of ownership etc and the phone's unique IMEI number which is located inside the phone under the battery. They use this number to generate the unlock code for your phone.
They should provide you with instructions on how to enter this code into the phone.
Once you unlock the phone, then you can insert a new SIM card in this phone or sign up with another phone provider using this phone.

HOW I CHANGE MY NEW SIM TO ANOTHER SIM BECAUSE I FORGOT MY PIN CODE?

I WANT TO KNOW MY PUK CODE OF MY MOBILE NUMBER

Your phone is asking for a code because it is locked to only work with one phone company. If your new sim is from a different company, you can request the unlock code from your old company, they may or may not give it to you (tmobile usually does, ATT/Cingular usually doesn't). The other option is to use a unlocking service, you can find plenty on ebay. If you didn't change phone companies, your new sim card is most likely bad, have your phone company send you another one.