Ihave and LG Phoenic and their telling me that using it or not that it will need to be charged every 12 hours is this true?
Once the phone has stopped charging, it means the battery is already full and you can unplug the charger. If you don't have an idea how a fully charged battery icon looks like, you may refer to page 25 of the user manual.
Don't have the user manual? Download it from the LG Phoenix product page. Just click on the manual download link located on the right hand side of your screen. It's that simple :)