How to update firmware for US use.

You can find the battery on Amazon and other places and videos on YouTube for how to do it.

I just spent some time trying to find an answer for you, at first all I found indicated it's probably not an update-able issue, rather the fact that the US carriers no longer support the bands in use by the phone. More digging however led to the conclusion that it still can I found this. It seems to say a number of carriers DO still support the phone.

So, the usual route to make such a phone usable in the US (if necessary) would be to flash the manufacturer's stock ROM for the particular carrier if available, in this case probably AT&T where you could, if they sell the phone, get the appropriate ROM to download. Or from Nokia a stock version for the exact model you have as well as in US English. On XDA and other places I found that yes, there are actually several options to upgrade your OS, should you wish to do so, KaiOS, Android and a couple others. I'd check with your carrier first and see if they have a ROM for the phone and that, yes, whatever you plan to do, will work. Flashing a new OS is not risk-free though so the ball is in your court. It may work as is with a new battery, or you might want to stick a newer or preferred OS in the puppy, I've done that several times and won't discourage you, just be careful, understand every action and have everything you need before you begin... You CAN brick it if something goes wrong.

Good Luck.

It sounds like you're encountering a firmware-update barrier with your setup. A good first step is to check compatibility ensure your device’s region (US in your case) and version matches the firmware you’re trying to install. Next, back up any critical data before proceeding, since firmware updates can erase or corrupt data if interrupted. Also, make sure your network connection is stable and you’re using the correct USB or interface cable (a bad connection often causes failure).