Inadvertent In App purchase - How to Cancel?

Dear Community,

I have an iPhone app called Shakespeare. I searched it looking for a quote from The Tempest when I must have clicked an In App button by mistake. I quickly pressed the home button to get rid of it but instead it read my fingerprint and charged me for the purchase with a message saying, 'If you use this app within 14 days you will be unable to cancel'.

I am might peeved about it, it was very sneaky. I have no idea if the payment of £9.99 is a one off or monthly, neither do I have any idea what the In App does, how to access it, how to delete, or anything. Very frustrating but I will immediately disable touch ID purchase from my settings so it doesn't happen again.

In the meantime what would be the best way to apply to Apple for a refund and to make a formal complaint? I'm hoping Apple will respond positively as undermining user confidence isn't in anyone's interest.

This might have been a perfectly above board procedure by the Shakespeare app, but I'm not a rookie user so can't understand why the process from accidentally touching the In App purchase (I'm assuming that's what happened), to the payment being made by touch purchase was quite literally just a few seconds.

Thanks for taking the time to read this.

K