How to use the MVG ticket machine

I wanted to buy the Monatskarte for March for U-bahn today. Usually I go to Hbf or Karlsplatz since they have big Automat with the "Monatskarte" option. But today I discovered that there is automat-looking thing at every U-Bahn station (not the ones accepting coins, but the one that accept only EC-card or credit card, looks like a ATM machine). So I happily put my thumb on the screen and tried to buy the ticket - didn't work. It asks for 5-digit "Kundenkontrolliersnummer", what the heck is this thing? Do I have to apply for a control number from MVG?

I have a green card so I don't need a Kunden number- but I am sure if you look at your old slips, there is a number written on them, and should be the number to enter. It gives you then the proper rings you need.

Found the number! Thanks!!

I use these automats to buy my ausbildungs tarif and the grüne karte. The number that you need if you have an ausbildungs tarif (this orange card with your photo on it) is written on the inside lower rigth corner. Usually the first two digits are printed and the last three are hand written over a set of five white squares. It should also be written in your old tickets.
I hope this works. Good luck!!

You don't have to have a Kundenkontrolliersnummer in order to get a Monatskarte from one of those machines. You just press the option that says you don't know what it is and then it asks you further questions like how many rings you want. That number is just so that it automatically chooses what you had last time.

hmmmm that I didn't know

thanks everyone, will try again today.

You can get them out of the ones that accept cash as well. AFAIK they don't ask you for a number at all.

just got the ticket.