You can change the sender name by setting the "sender_name" parameter as documented here.

This feature is disabled by default. To enable, please click on "SMS Rebranding" in the Developer Portal. You may need to submit some documents.

Note: There are 
restrictions on the use of SMS rebranding such as the countries supported and the characters permitted, please kindly note that we just guarantee this feature works properly in local Singapore. For the outside Singapore, their telco has their won regulations where all international traffic they will append their own convention