There is no right to prematurely cancel the internet in case of moving as long as the contract can be fullfilled at the new address - so it'll move there even if there is already another internet connection.
The only time when a premature cancellation is possible by law if the contract cannot be fullfilled at the new address, e.g. because the chosen speed cannot be achieved or the connection technology is not available (e.g. no vodafone cable access for a cable contract, no DSL avaiable for a DSL contract). In that case the contract ends with a 3 months notice period starting from the date the cancellation is received or the day you move (provided by official documents), the later one counts.
Additionally to this by law granted right for a premature cancellation, Vodafone accepts premature cancellations in the case that there is already another Vodafone contract (but ONLY a Vodafone one) in the new location - then Vodafone will end the "lower" of the two contracts also with that 3 months period from the moving or notification day (as above, the later one counts).
