call forwarding hacked

My call forwarding was hacked recently and my phone was diverted to another number to enable an attempted fraud on my bank account. Fortunately my bank realised the transaction was fraudulent and stopped it, however, everyone I have asked about fraudulent call forwarding from an iPhone has never heard of it before. I went into an Apple Store, my mobile operator and my work IT department but All seem perplexed and said it couldn't happen but it happened to me. My phone is always in my possession and is locked with a PIN. I did tend to leave it on wireless at home and work, both of which were secured, but Bluetooth was always switched off. I now only turn my wireless on when required.

Has anyone ever heard of an iPhone being hacked via Wi-Fi and call forwarding being switched on? I have searched online but can't find any articles to suggest it is possible so I am at a loss to understand how it happened.

I would appreciate if anyone out there with a more technical understanding of iPhone security could shed some light on this.

Thanks