Am using samsung galaxy y phone. I rooted it and installed Jelly Blast ROM in it. Also i changed the kernel . Now the problem is i can't be able to able to update my OTA even though a current update is available. My ROM is JELLYBLAST V3 and version is 3.0.0. Please help me hot to update it correctly.
Over-the-air (OTA) updates from your carrier or manufacturer cannot be directly applied on a device that has a custom ROM installed. This is due to many possible incompatibilities between the stock firmware and whatever code base the custom ROM is using. Therefore, most (if not all) custom ROMs intentionally disable any OTA checks that usually come standard with stock firmwares.
That said, some custom ROMs (e.g. CyanogenMod ROM) have developed their own OTA services. These are usually pull (i.e. phone checks for available update periodically) as opposed to push (manufacturer sends a message to phone to go out and download an update,) but generally work fairly well. You should contact your ROM's developers to see if such a feature is available for you.
Alternatively, you can try to return your phone to its stock firmware, and then you'll be able to accept the carrier/manufacturer OTA update.