I can vouch that many people have withdrawn what amounts to substantial figures from Entropia.
The withdrawal periods are usually quite lengthy, but they go through.
I'm not sure what information you have on file that does not match the in game values that you can't change via your entropia universe account login... I was fairly sure last I looked that I could set up and change the credit card I am using, the bank account details, etc.
Although I must admit I've never tried to change the actual bank account linked to the game as far as I recall.
Assuming you sent your details track and trace and can confirm they were delivered, then I suggest you simply open a Support case with MindArk to confirm that they have your paperwork and ask what the status is on getting the details updated or if there is anything else you need to supply etc.