Did you pay via iTunes/Google Play or directly to Optus? If it was via iTunes/Google Play then you need to contact them.
If you paid Optus, then you'd need to call 133937 or use their live chat service to request a refund - http://yesopt.us/chat2us
Yes, all depends on how you paid for it Ceciarum.
Check out Optus Sport subscription for more info.