How can I remove my iPhone 7 plus from this case without damaging my iPhone?

I am unable to remove my new iPhone 7 plus from this case. No instructions came with this case and the manufacturer does not list a phone number on their website for support. When I called Apple they advised that I go to the Apple Store to have it removed. Any other advice is appreciated. I bought this at the Apple Store and the salesman at the store installed my new phone in this case. I feel that this case does not provide adequate protection for my phone but wonder if I am stuck with this case since I can't remove it.

Decoded Leather Wallet Case for iPhone 7/Plus

Decoded Leather Wallet Case for iPhone 7/Plus

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