If you in set sim but gives amessage that there is know sim

There are four possibilities available.
1.Check your sim whether it's properly inserted or not
2.There may be a problem in your sim card so try another one.
3.Your mobile locked to particular network provider.
4.You mobile phone receives weak signal from near tower so try to Switch off your mobile,wait few seconds and switch on.
If your problem persists,Your mobile phone restricted by some network.So try to unlock your mobile phone.You can unlock your mobile phone using network unlock code.It's the best way to unlock your phone.If you need an unlock code for your phone visit Mobileunlocksolutions.com I hope it will be very useful to you.