My own opinion
just dial 44555 and vodafone will send a text to ur fone.
Or
If you are new to us on a contract, then the command you have been given above will not work for you as it is a Pay As You Talk command.
For contract customers 44555 is the unbilled balance checker service.
As you are new to us this may not show your unbilled usage until the first bill is printed and so ringing 191 as PICNIC has explained would be the best option for you. Any of my colleagues on 191 are available 24 hours a day to be able to access your account.
Otherwise, if you would like to access Online billing via https://online.vodafone.co.uk/dispatch/Portal/appmanager/vodafone/wrp?_nfpb=true&_pageLabel=Page_Registration_Service_Seam&pageID=AR_8001&FLOW=REGISTRATION,
Then you can register for this service by clicking on the link.