Prashant,
What version of code is your phone currently running?
If you look in the release notes for 9.3 SR2 there is a statement:-
For all SCCP firmware upgrades from firmware release versions earlier than 8.3(3) to Version 9.3(1) or
later, you must first upgrade your phone firmware to an intermediate version (8.3(3) to 8.5(2)) and then
upgrade to 9.3(1).
http://www.cisco.com/en/US/docs/voice_ip_comm/cuipph/7900_series/firmware/9_3_1SR2/release_notes/P790_BK_R345967C_00_rn-9_3_1sr2-7900-series.pdf
You may need to perform a two stage upgrade.
Hope this helps,
Craig
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