Believe iTunes account has been hacked. All credit has been spent on in app purchases which i haven't authorised HELP

I recently received an email from Apple informing me of unauthorised purchases made on my itunes account. I did originally question the authenticity of the email but after much analysis I was happy that the email was genuine. However, I immediately responded to this by changing my password on my Apple account to prevent anymore unauthorised purchases. At four in the morning UK time I received another email informing me that two payments of £5.99 and £2.99 had been spent from my itunes card on in application purchases (The application is named Kingdom Conquest which I have never been associated with so I obviously panicked.) Firstly may I start off by saying that this happened after I changed my password, signed out of my Apple ID accounts and switched my iPod to airplane mode and haven't used it since. I also removed my home address, changed email address and password again only to receive another purchase on the now old email address. I have tried clicking on the report a problem option but as I'm on a tablet i can't access itunes. I feel as if there is nothing I can do as I cannot access a authorised, working computer to track these purchases or to use iTunes. These suspected hackers have wiped my account credit and I have no clue what to do next. If anyone can PLEASE advised what to do or how I can protect myself further, thanking you all in advance!