Bought a key on InstantGaming and it's already used

Hello, i recently buy a key on "InstantGaming" website, i recieve it but when i put it in the EAapp an error message tell me that the key is already use... So, I ask the InstantGaming support to help me and they told me to ask EA the exact date and time when the key was used. Can you help me and tell me where I can have this information and who I need to ask cause they just didn't tell me ?

I told InstantGaming that this problem is their responsability and that they are suppose to solve it by them self but they just respond me a stupid automatic message.

Thanks.