Bill value constantly increase

[AntonnotnA]

Hello,
I use Young M for a first year. And Red inthernet in cable 50. My problem is that the value of biils for mobile internet and cable's one are also increse in significant value.
It was 12 euro in November. 28 in December and now its 37. Monatlich costs change constantly, some new options like "Sonstiges", "Verbindungspreise und Services" was added. And I have no idea what is it because I don't use any additional functions and don't order them. Also the value of discount's always changes from -20euro to -5 euro.

As I'm concerned I have to pay the same sum of money monthly for a year then this sum should be increseased in the next year. Explain me please why the values in bills are so unpredicatbly fluctuate  every month and ufortunatelly not in py profit.
Kind regards,
Anton

@AntonnotnA  Community-Team: Removed Screenshots due to customer details. Moved in the right board.

[MichaelBeyer2]

If you use features in your contract which cost money - like telephone calls in other countries or premium call numbers - you will simply  have a different or increasing bill every month (depending your usage). 

[AntonnotnA]

    But for example in December I didnt use anything except internet, and phonecalls inside the country.
and the bill anyway have been rise comparing with November. May I order more precise detalisation of my bill?
And why discounts always chaging?