LG VX-8500 Chocolate

So I bought one of these Sandisc micro chips that go into the right side of the Chocolate phone because I was getting tired of having to delete my text message box every 5 minutes since it only holds 50 messages. I was told that by doing this it would make it so I didn't have to do that, but I put the card in and it still makes me delete my inbox after 50 messages. is there some special thing I have to do to make my text messages save to this chip instead of my phone's memory? can someone please help me out here?

thanks
chelsea