I know nothing about mobile 'phones. I was perfectly happy with an ancient model that let me enter the 'phone number and press "call". However, a friend, taking pity on me, gave me an iPhone 3GS. A few days ago there was a screen displayed on the 'phone telling me to upgrade to iOS 6.1. I did as I was told.

Now the 'phone is useless. It has a battery life of just a few hours when not even being used.

I've had a friend check that I'm not running any unnecessary things.

From what I can tell from searching the internet, Apple doesn't allow you to downgrade iOS versions. Such a downgrade is only possible if your 'phone is jail-broken and you have copied some "blobs" - whatever they are. My 'phone isn't - I wouldn't even know how to do that.

I'm furious that Apple has ruined a perfectly good, quite expensive (at least by my standards) 'phone.

Is there anything I can do?

You can revert it back to previous ios but takes abit of know how I just done this with mine yesterday google has step by step instructions.

Any chance of a link? All the instructions that I've seen from googling require (i) a jail-broken 'phone, and (ii) previously backed up blobs. I have neither. I've also read that because it's a 3GS which has a different chip, most downgrading instructions won't work for it.

https://iphonetips4free.wordpress.com/2012/10/08/downgrade-3gs-without-shsh-blobs/

https://iphonetips4free.wordpress.com/2012/10/08/downgrade-3gs-without-shsh-blobs/

Wow if that works it's good news for 3GS users.

iOS 6 unfortunately has bad battery life, a trend that started with iOS 5. IMO the 3GS will be happiest with iOS 4.x on it.

6.1.2 just came out and fixes some battery issues, but not all.

I use a iPhone 3g and just set it back to os3.1.3 2 days ago no need to jailbreak and took 10 minutes one I had downloaded the firmware files bit strange on the 3g there is no Internet tethering if you run it on os4.2.1 but revert it back to 3.1.3 and the tethering option comes back only problem is half the apps don't work now , think it's about time I traded up

Here is link to what I use

http://lifehacker.com/5572003/how-to-downgrade-your-iphone-3g-from-ios-4-to-ios-313

obviously you don't want 3.1.3 so just download the os you want and restore from instructions , it will wipe everything of your phone though