IPhone 4 - No Sim Installed

[alwaysursram]

Hi
I got an Iphone 4 32GB - Gevey Sim. It was an unlocked Phone. I was planning to sell it and hence i did a reset and when it switched on it was showing me the itunes picture and telling that "Insert a valid sim with no pin lock to activate IPhone" Can you please tel me how to activate it. I have an AT&T Sim and Gevey Sim

Thanks