You stated this is a GSM device - the pictures you have are of the Sprint Galaxy S2 EPIC 4g SPH-D710 - this is not a GSM device - that would be CDMA. Please verify which device you are trying to auction.
Since there are several variants of the galaxy s2 - what is the model number of the phone? You can get it from the Settings - About Phone section or it is printed on the white label under the battery. Thanks for your time.