Paid Flight Rebooking.

I booked a Flight a while back which i missed due to late check-in. Ive sent through a Email to the address listed as i was told i couldn't get a Refund i could only use the Trip on another occasion which i would like to take advantage of now. Cause it was paid for. SAA hasnt responded instead sent a email stating that a Agent will be intouch. All i would like to do is get what i paid for nothing more nothing less. And with this Economy we cant let funds just go unsued.