Charged multiple times for in-app purchases but support won't help.

I contacted support after being referred to them by an app developer (nWay). On multiple occasions I was charged 2 or 3 times for one purchase of a £4.99 in-app item. I have PayPal as my payment method so the invoice comes through instantly. I sent screenshots and copies of the invoice to nWay and they confirmed that I had been charged multiple times and to contact Apple, as they handle the "real money" transactions.

The iTunes advisors I've been emailing have told me that, after investigating, they cannot see any duplicate charges, only that I have made several purchases. The last part is true, I have bought lots of things. However, on several specific occasions I was overcharged for purchases for this particular game.

I sent them copies of the PayPal invoices and all my discussions with the developer, the last of which states "upon further investigation, we have found your purchase was indeed charged 3 times". Not only that but the developer also told me in messages that their team was aware of the "overcharging issue" and were working to fix it. So, how long that had been going on for, or how many people were affected, is another question entirely.

Yet still, iTunes support are sending me the same cut and paste response saying they simply can't see anything (which is astonishing as I've attached loads of evidence). We've now reached a stalemate and they've told me they'll no longer reply as they consider the matter closed.

I literally can't provide anything that more clearly demonstrates and proves the overcharge:

• Confirmation from the developer that I was charged too much.
• Confirmation from the developer that they acknowledged this was a known issue.
• Screenshots of the game at the point of purchase showing I had only bought 1 out of a maximum of 4 of a certain item, yet had immediately been charged for 3.
• Copies of all the PayPal invoices with times and dates.

How on earth can I escalate this, as it's wildly inappropriate to shut down communications in that way.