Edit- use the same method but replace all EL30 with FC09
First off so everybody knows, feezing system updates did not work... neither did just installing the el30 modem... but this did... Ok this is very easy! Let it try to install... obviously it will fail because you are rooted... now you should see an exclamation point... just pull the battery and reboot! No more nagging message from your phone to update! This will work regardless of if you are on the el30 modem or not.... I have done it with the ei22 modem, el30 modem, and the ec05 modem and haven't had the update prompt after doin this...
Edit- after the battery pull and reboot don't panic if it throws you into cwm upon reboot, just reboot from there and you're good to go! LIKE ALWAYS MAKE A BACKUP!
Edit- for everybody getting the update a few days after doin this try this (fix by toadlife)
The update notification will probably stop if you modify the build.prop file to trick the phone into thinking it already has EL30.
Try this:
Open up a root shell and type the following (via adb, or a shell app)
su
remount rw
sed -i 's/SPH-D700-user 2.3.5 GINGERBREAD EI22 release-keys/SPH-D700-user 2.3.6 GINGERBREAD EL30 release-keys/g' /system/build.prop
sed -i 's/sprint\/SPH-D700\/SPH-D700:2.3.5\/GINGERBREAD\/EI22:user\/release-keys/sprint\/SPH-D700\/SPH-D700:2.3.6\/GINGERBREAD\/EL30:user\/release-keys/g' /system/build.prop
remount ro
I would recommend adb so you can copy and paste. Typing that might take awhile. 
Sent from my SPH-D700 using Tapatalk
First off so everybody knows, feezing system updates did not work... neither did just installing the el30 modem... but this did... Ok this is very easy! Let it try to install... obviously it will fail because you are rooted... now you should see an exclamation point... just pull the battery and reboot! No more nagging message from your phone to update! This will work regardless of if you are on the el30 modem or not.... I have done it with the ei22 modem, el30 modem, and the ec05 modem and haven't had the update prompt after doin this...
Edit- after the battery pull and reboot don't panic if it throws you into cwm upon reboot, just reboot from there and you're good to go! LIKE ALWAYS MAKE A BACKUP!
Edit- for everybody getting the update a few days after doin this try this (fix by toadlife)
The update notification will probably stop if you modify the build.prop file to trick the phone into thinking it already has EL30.
Try this:
Open up a root shell and type the following (via adb, or a shell app)
su
remount rw
sed -i 's/SPH-D700-user 2.3.5 GINGERBREAD EI22 release-keys/SPH-D700-user 2.3.6 GINGERBREAD EL30 release-keys/g' /system/build.prop
sed -i 's/sprint\/SPH-D700\/SPH-D700:2.3.5\/GINGERBREAD\/EI22:user\/release-keys/sprint\/SPH-D700\/SPH-D700:2.3.6\/GINGERBREAD\/EL30:user\/release-keys/g' /system/build.prop
remount ro
I would recommend adb so you can copy and paste. Typing that might take awhile. 
Sent from my SPH-D700 using Tapatalk
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