A customer who gets the same appointment reminder twice within a minute usually assumes the business is disorganised, even though the real cause is often a webhook firing twice or two Zaps reacting to the one event. The customer only sees the result, a duplicated text landing in their messages.

OnceOnly sits ahead of the step that actually sends anything. Its check and lock action checks whether a particular key, such as an order number or a booking ID, has already passed through this Zap. If it hasn't been seen before, the run continues and Mobile Message sends the text as normal. If that key has already been locked, the Zap stops there and nothing more goes out, so the same event can't trigger a second message.

The result for the person on the other end is one clear text rather than a confusing repeat, and for the business it means fewer replies asking why they were messaged twice. Connected through Zapier, OnceOnly can sit in front of any Mobile Message step in a workflow, whether that's a text triggered by a new order or one that reacts to a delivery status update, and quietly stop the duplicate before it reaches the send action.