Unknown charge by Vodafone in bank invoice

[AVD]

I created a new contract with Vodafone in the first week of March in the Vodafone Kabel Saarbrücken branch. The technician appointment was set up for the end of the month on March 31st i.e. I did not use ANY Vodafone services for the month of March. My contract has a standard DSL plan of 19,99 Euros per month. 
However, I see a deduction in my bank balance in March for an amount > 50 Euros. I would like to know what this charge is for (or whom I can contact regarding it), and if I can get a refund for this amount (since it is not a part of my plan). 

[Norman]

Hi AVD,

i'm sorry for that. 😞

Let me take a look. Send me a private message with your costumer number, full name, full adress, date of birth and the last 4 numbers from your IBAN.

I'll get back to you asap. 🙂

Best regards,

Norman