Do I need a dedicated number?
When you sign up, by default your account will send out using a shared number. If you want to purchase a dedicated number, you can do that from the dashboard here: https://dashboard.clicksend.com/#/numbers/sms
A Shared Number/Fixed Number
When sending an SMS, we will assign a shared sender number. This allows the end user to reply. Other clients also share this 'from' number. You have to send an outgoing SMS before the user can reply.
A Dedicated Number
Another option is to use a dedicated number that you purchase from ClickSend. This also allows the end user to reply. Only you own this number. You don't have to send an outgoing SMS first for a user to reply. You can advertise this number for keyword promotions etc.