Sigfox Integration and Call Processing

Hi, A simple diagram showing the integration. My understanding:
Start Sigfox Plug-in - Create Device - do Call processing later - SAVE; setup callback on Sigfox back-end.
Some documentation says you need to create a bucket, some say it gets auto provisioned.
I messed around and now have a dashboard and the devices are connected, BUT the data is NOT decoded.
I have multiple devices requiring different decoding. The simplest one simply changes state to show if the device is wet or not (leak detection) and the data changes between 2 states: 55 (no water leak) and aa (water leak), all other bytes can be ignored. Now whilst I have some idea of Python, I haven’t found any useful documentation on the Call Processing - can someone assist - it seems like the simplest problem.
Of course once it works I’d like a Telegram message sent to my client - I have used the Telegram Botfather before, so that shouldn’t be a problem.