Shiptheory can return tracking numbers back to orders in OnBuy once labels have been booked with carriers.
This behaviour is enabled by default. You can disable it from the advanced section of your OnBuy settings page in Shiptheory. The advanced settings can be found in the bottom left corner.
It is important to note that the order in OnBuy will be marked as "Dispatched" if a tracking number is returned. If you disable tracking numbers, the orders will not be marked dispatched. It is not possible to detach the two events via the OnBuy API but you can later manually mark orders as Dispatched via the OnBuy user interace.
If you have any questions regarding shipping with OnBuy, please reach out to support.