My wife has an iPhone (3s I think) and uses a new SIM from a Carphone Warehose phone, which she recently bought. It is with Talk Mobile

(It was cheaper getting a package, rather than just a SIM)

Everything was fine, she could use wi-fi at home and used her data allowance while out 'n about

Yesterday she noticed there was an upgrade of software icon on her phone, so she did this.

Now, when she tries to go on the internet, it does not work.

What setting must she change please, and just as important how do I find and input the settings.

thanks

Settings>General>Reset>Reset network settings

You'll need to re-log on to any wifi connections you use ie home as it also wipes the passwords stored on the phone.

After you get it working go into General>About to see if it downloads any new carrier updates. Sometimes solves data issues.