Samsung U-740 messaging memory

Hey i just got the u740 for verizon and im quite the avid txter. Getting to my 50th txt i recieve a message about how my phone does not have enough memory. Also when i check my overall phone memory it says that i have only used 5kb of my ~50mbs on my phone and have 10mbs total used on other crap. Is there an option to set it so my messages have no limit or do i need to get a microsd for this? thanks ahead of time.

as far as I know there is no way to store any more messages. There's an option to auto delete the messages however.