Thats one thing about "disposable" phones as the case may be.. These pay as you go phones are not meant to keep fully updated. In fact they want you (StraightTalk, Tracfone etc) to come back and buy the newest/latest model. So you may not get an update message from StraightTalk.
However, seeing how your phone is a Samsung, I would suggest viewing the official Samsung site for possible updates which you should be able to implement. Lastly, As a Tracfone user myself, I've attempted to update several software programs within my phone only to be told these can't be updated.. So unless StraightTalk tells you or allows you to update.. you'll have to start looking for a new phone.