Why can't I upgrade on my Iphone 3G?

[teenyroute593]

My blackberry recently broke so now i am using my mums old iphone 3g and for about a week ive used it without a sim card in it because i ordered a new one and i was waiting for it to come. I just connected to my wifi and i downloaded loads of apps like bbm, twiiter, facebook, instagram, snapchat and a few games. And then when i finally got the sim card it wouldn't work. We then worked out that because my mum had been given the phone from where she works they had locked it. I then when to a local shop near me and they unlocked it for me (I think this might of been illegal but im not sure) but now when I got to download all the apps i used to have it told me that i need to update to ios4 or 5. But when i go to settings > general theres no option for software updates. I'm really pissed off because I don't understand how i was able to download all them apps before and I don't get why theres no option in my settings for software updates. Someone please help me ASAP!!!

[Char]

Hi,
iPhone 3GS don't update cuz of the software. Only 4 + will update past iOS 3. I had one and it never updated. Got very annoyed >:c . Did a bit of research... IPhone 3GS don't update. Also be careful cuz the break really easily (software inside) it's a common fault. Apart from that, have fun!!!!
Hope I helped

[Ry]

that doesn't make sense to me either because it should be there in general but you can try downloading iOS from iTunes and plug the phone into the computer and update that way