A better invite came in, and you kept the first plan anyway. That’s how people learn you’re real.

A commitment tested by a better option is the only kind that carries information. Holding to the first plan when something more appealing turns up tells the other person their time is not contingent on nothing better appearing. Almost everyone has been on the receiving end of the alternative and remembers it exactly. The reliability registers far more than the evening does.

Keep the plan you made, and do not mention the one you turned down. If you genuinely have to change it, say so honestly rather than inventing a reason. Reliability gets built out of small unremarkable evenings.