Samsung Rugby A837

when i would text on my old phone, and wanted to go back in the text info to change a letter of a word or fix a word, the right soft key allowed me to back track through my text message to fix or change things. Is there some way to do that on the rugby? I can't seem to figure it out, so I end up exiting my text and starting over. I know there has got to be a way, but I can't find it.
HelP!