Can't update settings on brand new iphone 5c?

I just got an iphone 5c today, it was a replacement because my last iphone was water damaged and unfixable. But Vodafone have texted me saying I need to update my settings to use the internet and given me a link to download them from. However I can't connect to the internet wirelessly to open the link as the 4g doesn't seem to be working and safari says it can't connect to the internet. Any help? Why isn't 4g working?

Go into settings, go to cellular, turn on 3G/4G, if that doesn't work then I can't help