Hi @gmar,
welcome to our English Community. Nice to meet you here.
You have a question concerning your bills. If I understood you correctly, you would like to know why you received the extra billing only for the last 3 months, right?
Please note that you only receive an extra billing (Einzelverbindungsnachweis) if you have connections outside your flatrates like special numbers, subscriptions, foreign connections and so on.
It can also be that you did not activate the extra billing from the beginning.
I hope I could completely answer your question. If you have any further questions, just feel free to come back here.
By the way, we now have also some features for our English-speaking customers. Just have a look here:
Loving greetings,
Tobias