Default Please Help Me Update Android 4.4 on My HTC One ATT

I live in VietNam, i use a HTC ONE AT&T, I have to unlock Sim to use in VietNam.

Before, i unlocked bootloader and flash a rom cook.

Today, i want update Lastest Firmware of Android 4.4 ( I using a version Firmware of Android 4.3 )

I flash Stock Recovery of ATT, locked bootloader, Run RUU RUU_M7_UL_JB43_SENSE50_MR_Cingular_US_3.17.502.3_Radio_4A.19.3263.13_10.38j.1157.04_release_334235 _signed_2

After, i go to Setting > ATT software update > check for Update, but it say : "no update is available for your device at this time. your device will automatically check for an update within the next 48 hours"


Everyone please say to me how to update lastest firmware but not S-Off (my device S-ON).
Send to me a file or link to download lastest Firmware.

i download darkboot_att_4.18.502.7.zip from a Post's member, but when i flash firmware : fastboot flash zip darkboot_att_4.18.502.7.zip
Ít say: Fail

Thanks you !