changing a trip

I have a trip round trip booked for 12 days upcoming. I wanted to change my tickets to a longer period and cancel the return flight. It appears I cant cancel the second part of the trip and need to make the new reservations for a one way trip then cancel the whole round trip. That triples the price of the trip. Do I keep the first part of the flight and then cancel the return trip or do I just no show. The flights are all on SWA.

Charlie NH

Chakat- Not to be flippant, just call Southwest and they will explain what you have to do and will walk you thru the process, if you want.