Once DLT system go live then all sender ids will be approved by DLT portal only. Old sender ids will not work.
First you need to login to your DLT portal as Enterprise
Then click on headers >> SMS headers option.
Then click on add option
Then you will see Sender ID request form:
For transactional SMS sender ID click on other.
Then type your six character alphabetic sender id related to your business.
Then click on search button, it will show if this sender ID available or not.
You can only request sender id that is available.
Then type explanation, how this sender id is related to your business / product / service.
Then click on submit for approval.
Operator will review and approve your sender ID within 72 hours.