Vodafone HSDPA contract period

Anyone have the T&Cs for the Vodafone ESIM Lenovo Data 250 tarrif? The
Voda site has for some time generated an error when you try to see
their embedded card T&Cs.

I ask because my laptop has s Sierra HSPDA card inbuilt, and I, of
course, activated it. It's a new toy, after all, I was curious, and I
thought (wrongly) that it would be useful for a tour around the
country that I undertook. A few months later I decided to cancel the
contract for the (I thought) good reason that it won't hold a
connection for more than a couple of minutes or so, so my £25 + vat
was rather poor value.

I have now had a bill with a £138 contract cancellation fee. I
remember no mention of a minimum contract term when I signed up, and
it seems harsh to enforce a minimum term when I had not (to my
knowledge) recieved any subsidy (although I suppose Lenovo may have
done).

Of course, I may have just not heard the 'minimum one year' bit when I
made that call activating the service. But then I also missed the bit
that said 'this device doesn't work'.