[ketzu]

No not necessarily. But it might be more cost effective to get the deutschland ticket if you can still get one for this month. (You don't have to get it from DB, some allow cancellation much later.)

Ticket sales are generally quite straight forward with DB online and the area tickets are usually a good value compared to local tickets.

[lxgr]

You can always get one for the current month and (except for maybe the last day) immediately cancel it with some sellers.

[usr1106]

D-Ticket is a subscription only sold for calendar months. The basic terms are set by law, but some sellers have more generous terms, that is allowed. You need to cancel before the 10th of the current month in order not having to pay for the next month. If you buy after the 10th you are charged for 2 months right away. Most sellers require a German bank account, but e.g. HVV supports Paypal (worked for me) and in theory credit cards (did not work for me). I don't know any seller that accepts cancellations after the 10th, but I have heard a couple should exist.