Hi Garima,
If it were the actual setting, you would expect to hear the slowed greeting play across the board (internally and externally). Here's the documentation that explains this greeting speed configuration:
http://www.cisco.com/en/US/docs/voice_ip_comm/connection/7x/release/notes/712cucrn.html#wp376504
If the above doesn't seem to be your problem, the easiest way is going to be to get a network capture right from the CLI of UC so you can then play back the RTP stream to confirm whether or not it's leaving the NIC slowed down (most likely the setting within UC) or if it leaves normally but arrives at the destination slowed down (something happening between the NIC of UC and the destination).
Hope that helps,
Brad