I purchased secondhand an AT&T HTC One (m7) that has been unlocked to enable me to use a SIM-card for a local carrier i.e Safaricom (Nairobi, Kenya). Since the purchase, there has been no software update available for my phone. A HTC Customer Service representative just informed me that the updates are sent by the carrier (AT&T) and since my phone has been unlocked from the carrier, I won't receive any updates. Is there a way AT&T can still send me software updates despite my phone having been unlocked by them from their service? If so, how do I go about it? If not, what can I do to get updates on my HTC One?
The issue is not that the device is SIM unlocked, not exactly. The issue is that you are using another carrier. OTA updates go out over AT&T's cell network, and since you are not using their network, there is obviously no way for them to "send" it to you.
You can still apply updates by downloading what is called an RUU (ROM Update Utility) direct from HTC. The RUU is downloaded to a PC, then you connect the phone and run the RUU (be aware that RUU will wipe user data). However, if you want the latest (KitKat) update, it has not yet been released yet in RUU format. It will be posted here, when it is available: