How to update my IOS software on a iPhone?

Right now it's at iOS 4.2.1. I need to update it at least to a iOS 4.3. I tried to google how to do it and it said to go settings>general>software update but I don't have iOS 5 so I don't have the software update button in my settings. Also my computer isn't working so I can't connect my phone and update the software. So my question is, is there any way you can update your iPhone 4 with and iOS of 4.2.1 without a software button or using a computer? Btw I'm only doing this because I accidentally deleted instagram and it requires an iOS of 4.3.So ya.

On your iPhone go to settings>general>software update

There's no way to update iOS <4 without a computer and working iTunes. Sorry the update setting is only available on iOS 5+

No. You need a computer to do the update.