Council tax - moving to 12 instalments

Hi - I got my 2013/14 council tax letter through the post a few days ago. As expected payments default to 10 instalments but I would like to take up the new option of paying it over 12 months instead. When I called the council they said they would only offer this facility if I moved to paying by direct debit. Can this be right? I thought this option would be open to all??

Does anyone out there know if I can challenge this?

Many thanks :)