Call 03333 040 191 from a landline (or another mobile). Calls are charged at exactly the same rate as 01 and 02 numbers are, which means they'll be free if you're calling from a landline with UK free calls or from a mobile phone with a package that includes free minutes. That number is available from 0800 to 2100 daily.
Are you sure that you've paid your bill? (You might, for example, be paying from a debit card but you've been issued with a new card, with a new number, and have forgotten to tell Vodafone).