I want to use a mobile phone as an mp3 player

There are three possibilities to get this type of issue.
1.There may be a problem in your Sim card so try another one.
2.Your mobile is locked to particular network provider.
If your problem persists,After replacing new Sim card means definitely Your mobile phone is restricted by some network so try to unlock your mobile phone.For unlocking you can approach your service provider or else try to buy an unlocking service from any one of the online unlocking service provider like Unlock-Zone.com Here you can unlock your phone at low cost.

Did you mean your phone shown no sim card inserted even your sim card present on your phone?
Yes,Means,There are three possibilities to get this type of issue.
1.There may be a problem in your Sim card so try another one.
2.Check your Sim whether it's properly inserted or not
3.Your mobile is locked to particular network provider.
If your problem persists,After trying first two ways means definitely Your mobile phone is restricted by some network so try to unlock your mobile phone.For unlocking you can approach your service provider or else try to buy an unlocking service from any one of the online unlocking service provider like
TheUnlockSpot.com

Did you mean your phone shown no sim card inserted even your sim card present on your phone?
Yes,Means,There are three possibilities to get this type of issue.
1.There may be a problem in your Sim card so try another one.
2.Check your Sim whether it's properly inserted or not
3.Your mobile is locked to particular network provider.
If your problem persists,After trying first two ways means definitely Your mobile phone is restricted by some network so try to unlock your mobile phone.For unlocking you can approach your service provider or else try to buy an unlocking service from any one of the online unlocking service provider like
Unlocking4U.com

There are three possibilities available to your phone shown insert sim card message.
1.There may be a problem in your Sim card so try another one.
2.Check your Sim whether it's properly inserted or not
3.Your mobile is locked to particular network provider.
If your problem persists after trying the first two steps means definitely Your mobile phone is 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 ProUnlocking.com I hope your problem will be solve by any one the above ways.

There are some possible solutions:-
1. Check that your sim card is in perfect condition by insering the same sim card in any other mobile phone... If the same message appears that means the problem is in your sim card
2. Check that your sim card's slot is in perfect condition by inserting any other sim in your mobile phone... Still if the same message occurs that means the problem is in your sim card's slot
3. Check that you are inserting your sim card correctly or not

Are you able to switch on your phone without the sim card i mean like in OFFLINE mode ? Or your simply doesn't boot up with the sim card inserted or you are getting any message like sim card failed and then phone goes off ?

Try inserting some other prepaid sim in the phone and see if it turns on, if that succeeds then there is possibility that may be your sim card has damaged.

Thanks !!

search google or another search engine for a website where you can get the unlock code for the phone. it's usually 20 bucks...but some carriers give you the unlock code for free if you email them depending on if you're a customer or not

Format ur Mobile -

Try your sim card to another phone, or try another sim to that phone just to eliminte the problem. Sim card are easily ruin by static discharge