S9 No system updates

[xfoneguy]

I purchased an S9 used, several months ago.  The phone is less than a year old.  I'm assuming that Samsung's warranty only covers the original purchaser?  I don't know how I missed it until now, but it has never had ANY system updates. The latest security update is dated Sep 1, 2018, and Android is still version 8.  I have tried every means I could find to manually update it, but nothing works - it always says "latest updates are installed" (or something to that effect).  I've tried connecting to Smartswitch on my PC, Cache Wipe and Factory Reset on the phone, etc. Nothing works.  This is the G960U model. An IMEI number check shows it was originally the Sprint variant, and is unlocked. I am using Cricket Wireless service. The phone itself works fine, but it appears that it can never be updated.  Also, I am getting a message that says "Activation Not Completed - Sprint OMADM" though as I said, it is activated with Cricket Wireless and seems to work fine otherwise.

I'm not sure where to go at this point - is this a Samsung issue, or a carrier issue or am I stuck with an un-updateable cellphone?

Any thoughts would be greatly appreciated. Thanks.

[BandOfBrothers]

My knowledge base comes from what happens in the UK @xfoneguy  but I'm assuming similar happens in your country. 

What you have is a branded Samsung phone i.e a phone that was supplied by a network that will have the original networks flavour of software on the phone even tho it's been unlocked to use other networks.

In the UK some Networks want to test a new software update before allowing Samsung to push the update out to make sure it does not clash with its branded phones and network services.

So the update comes via the way of the network authorising it.

If this was an unbranded Samsung phone then it would be Samsung that push it out without any interference via the networks. 

The Manufacturing Warranty follows the phone not the owner but an original proof of purchase maybe asked for in some cases.

Samsung can check the warranty status via the phones serial number.

As people buy and sell phones privately more and more nowadays it would be imo impractical to start restricting support for the phone. 

What you could do is look on the original networks forums to see if other users of your phone still on that network have received an update.

I'm sure a Samsung Service Centre or Samsung Experience Store would try to help too.

Other extreme options could be uploading a custom Rom onto the phone but please ensure your fully educated before attempting this.

Xdadevelopers website is a good place to look.

Disclaimer.

A person uploading a Custom Rom does so at their own informed discretion that can cause issues that affects the stability of the phone and or causes it to not work properly.