i have an international one way award on star alliance airlines booked on co.com

i want to change the dates, last time i tried with a similar ticket it would not let me change online. Due to my location it is hard to call and I don't want to use skype.

Should i just cancel the existing ticket online and book another one with the new dates? Will the miles just be redeposited and my CC refunded for the taxes? I am CO Platinum.

thanks