I have recently bought a new and unopened (i7-8GB-256GB) surface pro 4 on ebay. After purchase I am getting worried if 8GB is enough for me or not, so I want to see if it is possible to replace my device with a 16GB model and pay the extra.

The device is new and unopened and still in its 30 days return period but I am not the original buyer; though, I have all the receipts. Is there any way to do that?