Sprint Developers

Does anybody know if Sprint phones such as the Samsung A-900 will stream AAC+ audio along with video. If I send an audio only file with AAC+ and capture the resulting audio spectrum I see up to 20khz bandwidth in the int the audio. If I send in AAC+ with audio in a .3gp file and capture the audio, I am seeing a cutoff at approx 7khz. Does the phone do this purposely? Is there some sort of signaling required to get the phone to play the AAC+ ?? Thx for the help ....