Sim card not recognized - Galaxy Samsung Cell Phones

This may due to three problems,either the sim is not properly inserted or there is a problem with the sim or the phone may be locked with any particular network.Try to insert the sim in the correct position,try inserting some sim with the mobile and still if you get the same error then the phone needs to be unlocked to make it accept other networks.To unlock you can approach Simpleunlocking.com and get the unique unlock code for your Samsung mobile along with free unlock instructions.You need to specify the mobile model,country,locked network,IMEI and based on the availability you will receive the unlock code.