To conduct prepayment and for activation you need administration rights. To use Ckalender after the test period, you can comfortably and quickly activate the CCalendar service directly online with prepayment.
The same way you can even comfortably reactivate an expired prepayment up to days after expiration.

Therefore, as an logged in administrator, in CCalendar navigate to the administrator menu item "Configurtion/Payment".
Here choose your desired CCalendar functions and payment methods.
At the moment there are three possible payment methods available:

Payment method	Execution	possible from	Activation effects	Period for prepayment	Cancellation
per Invoice	manually, by admin	international	after payment receipt	6, 12 or 18 Months	unneccessary
per electronic debit advice (Single SEPA-direct debit mandates)	manually, by admin	all SEPA-compatible countries	immediately	6, 12 or 18 Months	unneccessary
per SOFORT-Überweisung / PayPal / paydirekt	manually, by admin	international	immediately	6, 12 or 18 Months	unneccessary
Contiuous subscription per yearly bank collection (yearly SEPA-direct debit mandates)	automatically, yearly	all SEPA-compatible countries	after signed SEPA form is received per fax or e-mail	Automatic bank collection and extension by 12 months respectively	written, before expiration of the current prepayment period

You can find further details to possible configuration options and prices under the menu item "Costs". At CCalendar there is no period of notice with manual prepayment! - You only pay in advance for the desired period of activation. When it expires, you as admnistrator will be informed by e-mail and can renew the activation if you like. If you do not want that, your account expires automatically. (Your data will be stored for days, in case you decide to renew your activation at a later date.)

Exception: If you chose the payment method "Continuous subscription" and issued a written collection authorisation, you have to cancel the continuous subscription x months prior to expiration of the current payment period in written form, if you wish to stop.