I just heard from iZettle about a rather unfortunate feature of the iOS 9.0 upgrade that Apple will be dumping on its fanbois tomorrow: it doesn’t work. No, I mean it really doesn’t work. There’s a bug that stops it pairing with some Bluetooth devices, including iZettle card readers.
If you’re the kind who has to have the latest iPhone or fondleslab then you’re going to have it set to auto-update. Bad luck. Will you take a cheque?