You can switch to a more comprehensive plan at any time after which it is directly active.
With only one restriction: a maximum of one subscription rate change per day is possible. The balance you have left from the previous plan will be credited to the current account and deducted.
Downgrading to a less comprehensive plan may only occur at the end of the previously selected subscription period and have to be carried out up to max. 14 days before the end of the contract period.