Normally, you would add or upload your contacts manually. You’d have to ask people for their mobile numbers and then upload the spreadsheet to your BulkSMS phonebook.
To make this process a whole lot easier, the Group Opt-in feature allows people join your contact list by sending a simple text message from their mobile phone. It’s that easy!
Please note that this should be tested before rollout to countries outside of South Africa and the United Kingdom.