M300 PHONE SAYS PHONE LOCKED RETURN FOR SERVICING HOW CAN I FIX

If it is network locked, you can remove it using unlock code, you can purchase such code from any vendors online like
http://www.superunlockcodes.com/samsung-m300/rs5wp9

HI if your samsung SGH-M300 mobile is locked by network provider .Then you can easily unlock it using sites like WickedUnlock.com here they are providing unlock code for all mobile models at reliable cost .You first check that whether the code is available for your country and network provider .If yes then pay for it and unlock your phone ....

Did you try turning if off and on?
If so, remove the sim card, wipe with a coarse dry cloth of some type, jeans are OK.
Then try it.
thanks

the lock code on my samsung m300 is the last 4 digits of my number. try that, also you can try 0000. that is all i can think of.

please hel me to unlock my cellphone samsung sgh-m300
imei:357453453/01/079288/5

If it will not let you eneter any more codes it is because the SIM card is blocked from to many tries and to many times of enetering the WRONG code. You are going to have to buy a new sim card from ATT- about $20

You could try to reset your phone.
Remove your sim card.
Enter *#2767*2878#

take out the battery when the phone is on and wait ten seconds then put it back in this is called a hard shut down it should restart you whole phone without losing any contacts or any thing

try this code hope it works for you

*2767*2878#

peace!

you should take the phone to a mobile center and have them unlock it for you.