I'm not sure what they're asking for, but if you could get any purchase receipts you have available those would definitely be good to send in. 

I have sent them screenshots of my recent purchase history, including order numbers and dates of purchase, three times now. They also want to know other things like Device model, month and year of registration (I wasn't sure if that was the month/year I registered my device, because there's no way I would know what month and year I started playing the game...).

Two days ago, I received another email that my request was escalated to "second-line support", whatever that means. 

8 days and counting...