Just drop by any nearby Digi Centre and they'll do it for you. For China Phones, you need to configure manually.
1. That supp line need to be with us for at least 6 months before you can request for that. Once you've exceed 6 months, just walked in together with the main line holder and request for your line to be separated from the main line. It takes 2-3 working days for them to separate your account, having said so your phone line will only be cut off for 2-3hours during the reregistration process. You may request for a courtesy call to an alternate contact number once they've reactivate your line so that you know when to restart your phone.
2. Turn on call waiting from your phone?