Yes! All Plans are prepaid.
As you send or receive a message the Price per message will be deducted from your Recharge amount according to the message type(Session or Template) depending on the chosen plan.
For Example: If you Opt for Plus Plan (₹0.18/ Session Message & ₹0.58/Template Message)
A User sends 5 incoming messages and your account sends 5 outgoing messages = 10 Total Session Messages, Here ₹1.8 Will be deducted from your balance.
Next, If you Broadcast messages to 1000 users after 24hrs of the user's last message or to initiate the first conversation. 1000 x ₹0.58 = ₹580 Will be deducted from your balance.