The 14 days rule you refer to is the Right to Withdraw ("Widerrufsrecht") but only applies to contracts that have been agreed upon using means of telecommunication (by phone, by [e-]mail, by fax, by Internet) or outside of a shop or office (like at your home). And the 14 days don't count from the moment the line is set up but from the moment you are informed about your right to withdraw - which can be quite days before the setup of the line.
There is no such right for contracts signed at a shop or office from Vodafone - they are final.
Anyhow as you say that the 14 days have already passed, you are now (finally) bound to the contract at least for the minimum contractual term (usually two years). And there's also no possibility to switch from landline to mobile...
