Most older styles of cell phones, such as flip phones and slider phones, that are Straight Talk compatible can use the $30 All You Need Plan, as of 2015. Smartphones are not compatible and must use the $45 plan.
A smartphone is generally recognized as a cell phone with a mobile operation system, such as the iPhone OS, Android, Blackberry OS or Windows Mobile. Some flip phones that can use the $30 plan include the LG 200 series and 420G as well as the Samsung T255G and R335C and Motorolla's 418G and razor V3A models. Compatible slider phones include LG's 290C, 620G and 511C along with Samsung's T404G, R455C and T401G. A complete list is available on the Straight Talk website.