Three network down (again)

I live in Gilwern, South Wales, and our SIM card internet is down (again). I've checked on the '3' website and it's the same old message, something like "we're sorry etcetc and we're working on it" but can someone please explain to me how my 'other' smarty sim (in my phone) is working ok and is, in fact, how I'm typing this on the iPad by tethering it to my phone?

Not happy (again)