How come I cannot activate 1511CALLBACK service?

ZONE Telecom > Business > 1511CALLBACK
Only ZONE1511 subscribers with their mobile number registered are able to use the 1511CALLBACK service.
 
If you have not registered your mobile number/s with us, kindly login to your account via http://www.zonetel.com.sg, click on “Manage Telephone Numbers” to update your mobile numbers. 
 
If you are not ZONE1511 member, kindly sign up at www.zonetel.com.sg.  Alternatively, you may contact us at Corporate Helpdesk at 6720 6726 / 6720 6727 or email us at customercare@zonetel.com.sg for assistance.