The Promotional SMS Service is for Businesses who want to send offers and promotions to their existing and new customers. It is configured by default for all new accounts. The SMS are sent to opt-in and DND numbers only anytime between 9 am and 9 pm only. You can start your free trial anytime.
Transactional Route of SMS sending is just used for sending transactional Smses such as bank alerts and OTPs to registered users. You will have your own 6 character Sender ID (Ex: VM-SMEDIA) to send messages. You just need to create an account contact Auto By SMS to configure it; you are not required to pay any setup cost for it.