Have you been in an official Vodafone shop in not a one of those "we sell all kind of crappy contracts" shops?
The Vodafone service team can see the outgoing calls and SMS over the last 90 days and in doubt e.g. for a law suit even produce a statement of all calls.
Call the service hoteline ( 0172 229 02 29, should be a free call in the vodafone network) or go to a Vodafone shop and let them call the CallYa service desk.
Sad thing is, that most of the shops are really bad in service and just trained to sell contracts and phones but not to follow up on or resolve customer issues. In 99% of the cases they will need to call the backoffice and get them to sort out the problem. But that is something they should - even without you pushing them for it.
Seems to me the just looked for a quick way to get rid of you, probably since they also didn't feel to comfortable speaking English? (still a big problem in Germany...)