It would help if you state which specific model you have. But first things first: is there an official update to that particular model AND region it was intended for sale? Even if an update is out for a device in one region doesn't mean it's out yet for another (and things get even murkier if this is a carrier-branded model).
Unless there's an official update available, you won't be able to get anything beyond what is already installed (assuming that's the latest available update).
You can try to install a custom ROM based off a newer version of Android, but you have to make sure the custom ROM is compatible/made-for your specific model or you might end up with a brick. Flashing custom ROMs, also, is not for the faint-hearted and you should know what you're doing before meddling on that or, again, you can end up with a non-working device.