You can't. The 8gb was never truly there to begin with. The memory was hacked so your computer read it at 8gb. Memory hacks are designed to fool your computer. They also appear to hold the 8gbs worth of data. In reality, it is only transferring part of the data or writing ghost files. Then when you try to play it, you get file format errors and player can crash.
Contact your seller immediately and if you bought it off of eBay file a dispute through Paypal. You should also sign the Petition against scammers and eBay on the main page.
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 ops: 1GB Black Hacked Chipod ops:
2 GB Black Temptation Player 
8) WHITE MEIZU M6 8GB 8) |