1. Do not want to receive calls? Type **21*999999#, then press the green answering key. If someone is to call you, he / she will hear ‘the number you dialed does not exist’, isn’t it cool? To disable this feature, type ##21#, then press the answering key again, and everything will be normal.
2. Get your keys locked in your car and get a remote control at home? Call home and tell anyone to press the unlock button and keep your mobile phone 1 foot away from the car, this really works.
3. Battery is going dead? Type *3370# and your cell phone is going to restart, and you can expect to see an increase of 50% in battery life level, now you can make any emergency calls. This only works for Nokia cell phones.
4. Get your mobile phone lost or stolen? Type *#06# and you will get your IMEI number, tell your service provider this number and they can block it. You will note get your cell phone back, but it will be useless even if the SIM card is changed.
Please note I myself have not tried all of them. If you have a Smartphone, some of them may not work for you. However, you can always type *#06# to find your IMEI number which can be found under the battery in the battery pack too.