If you moved to a destination where the contractually agreed services cannot be provided anymore (no matter if witin Germany or out of Germany), the telecommunication law requires you to pay for additional 3 months after your move. This 3 months period starts by the day your cancellation request is received, but the earliest with the day of your move.
So if you noticed Vodafone that you'll move in January -and- your movement date according to the official documents was in March, then you'll have to pay for these 3 months beginning with the date that your official unsubscribe letter states. This means if your document says that you left Germany on March 1st, you have to pay until June 1st (3 months from March 1st).
In case you moved out of Germany before your cancellation request in January, then it would be still those 3 months beginning from your initial termination request - meaning a cancellation request received in January for a move before that date would still require a payment until April. But this would only apply if you would've already moved out of Germany before your cancellation request was received by Vodafone.
By the way: Even with a regular cancellation, there is NO way to terminate a contract immediately - you have to stick to your contractual term (e.g. cancellation can only be written to the end of the term) and are bound to the notice periods (usually 6 weeks if the contract had an inital minimal term of 12 months -or- (most likely) 3 months in case the inital minimal term was 24 months).
So in none of the constellations given above, you'll get a reimbursement for Feburary or March if you sent your termination request in January.
