There is on some phones.
Try reading the manual thoroughly.
If that doesn't work, put up some more information on this question such as phone model, type, and service provider.
Otherwise, nobody on this world will be able to help you.
Depending on your phone and service provider, your menus will be different, so there's a couple different ways. I have verizon, and I have to go to menu>messaging>settings>font settings. You might have to go to menu>settings>messaging>font settings. It all depends how the menus in your phone are set up!
