With the help of the following tips written below , half of your problems have been solved especially those that are using non android devices .Also some tips here will serve as a guideline in learning.. Some common codes/problems & solutions are 

**HOW TO KNOW
ORIGINAL PHONE AND A FAKE PHONE
Before you buy a new phone dial *#06# ,it will display the serial number or IMEI number which must be 15 digits and must begin with 35. Now check whether the number displayed is the same with the number on the battery base. If it’s original the numbers would be the same, if fake the numbers would be different. You can check your phone right now to know whether you are using original phone or fake phone.

**HOW TO BLOCK SOMEBODY FROM CALLING YOUR NUMBER.
Dial 350000THE PERSON’S NUMBER#SEND. From then on the person will not be able to call you again
with that number. Dial *350000# to cancel it.
Remember if you have barred more than one person when you dial 350000# it will cancel everybody you barred.

**HOW TO MAKE SOMEBODY PAY IF THEY FLASH YOU.
If somebody is flashing you and you want to make him/her pay just dial **21*171NUMBER OF THE FLASHER#SEND. From then on if the person flash you again his/her money will be off. Please don’t use this code to wicked somebody unless you have told the person not to call you again. To cancel dial
##21#SEND. Remember for some phones ##21#SEND means to bar all incoming calls. Don’t use these codes if you don’t know what you are doing.

**HOW TO LOCK AND UNLOCK YOUR CREDIT.
With this code you will be the only person to make call from your phone. Nobody will be able to make call from your phone even if you have credit.
To lock dial **0333000002213#SEND
To unlock dial **032213#SEND

**HOW TO CHECK YOUR WAEC RESULT WITH YOUR PHONE.
Go to text message. Type WAECYOUR EXAM NUMBERPIN NUMBER ON YOUR SCRATCH CARDYEAR OF EXAM
send to 32327 . Wait and you will get your exam result.

**HOW TO RETRIEVE YOUR STOLEN SIM CARD.
First, buy a new SIM card then call the customer care of your network. Give them the following informations: THE MOST 3 NUMBERS YOU CALL, THE LAST DAY YOU RECHARGED YOUR PHONE, THE DAY YOU LOST YOUR SIM. They know all these informations and once you have answered correctly they will put your line back to your new SIM.

**HOW TO ANSWER YOUR CALLS FROM ANOTHER PERSON’S PHONE IF YOUR BATTERY IS LOW OR YOUR PHONE IS OFF.
Before you totally run out of battery dial **21PHONE NUMBER OF THE PERSON YOU WANT TO RECEIVE YOUR CALLS FROM#SEND
From then if somebody call you it will ring on the person’s phone you have put. Cancel it any time from your own SIM card by dialing ##21#SEND .Remember if you don’t have battery on your phone at all you can also remove your SIM card and put it into another person’s phone then put the code. In any case always dial ##21#SEND from your own SIM card to cancel it.
IF YOU CANNOT RECEIVE OR MAKE CALLS AND YOU WANT TO FIND OUT IF YOUR PHONE IS OK.
Dial #3300000#SEND to cancel all call barrings.

**HOW TO STOP SOMEBODY FROM MAKING INTERNATION CALL FROM YOUR PHONE.
Dial **330000#SEND
To cancel dial #331#0000#SEND
HOW TO HIDE YOUR PHONE NUMBER BEFORE MAKING A CALL.
Dial #131#THE PERSON’S NUMBER then SEND.

*#IMPORTANT TELECOMMUNICATIONS/COMPUTER ABBREVIATIONS YOU SHOULD KNOW.

GSM: Global system for mobile communications
PMB: Per munite billing
SIM: Subscribers identification module
DC: Direct current
BAIC: Barring of all incoiming calls
IDD: International direct dialling
PIN: Personal identification number
BI: Basic information
OSS: Operation and support sub-system
HLR: Home location register
SMS: Short message service
ISDN: Integrated service digital network
PC: Personal computer
PUK: PIN unblocking keys
PTC: Private telecommunications center
MRF: Mobile radio frequency
IMEI: International mobile equipment identity
CUG: Close users group
MCC: Mobile country code
CW: Call waiting
PSB: Per seconds billing
MMS: Multimedia message service
WAP: Wireless application protocol
HTTP: hypertext transfer protocol
OTP:: One time password
USB:: universal Serial Bus
ROM: Read Only memory
RAM:: Random Access Memory..

I believe this information will help out