Your sim card is rejected by your network service provider and you should contact to your network service provider,if not solved, go to Nokia Care Center.

Hi,
If the rejected sim card belongs to a different carrier, then your phone may be locked to its network!!!Inorder to use other carriers, you should first unlock your phone!!! Though there are many methods to unlock a phone, unlocking using codes is easy and the safest method!! You can get the codes from your service provider or from reliable online sites like ****

Is the sim for a different service than the one you used previously?

i am not able to reopne my nokia 2310 it shows sim card rejected.