How to pay my bill?

[iiooiiooiiooii]

Hi! I need help understanding my invoices. I get invoices but they refer to "credits" - which recently went negative. There was no "Zu zahlender Gesamtbetrag" and bank details either. Does that mean there's no need for me to pay yet? 

Also, how can I make sure my SEPA Direct Debit is turned on? I don't wanna miss the bills because I don't understand the invoices. 

[Torsten]

If you have issued a SEPA direct debit mandate, the invoice amount will be automatically withdrawn from your bank account about a week after the invoice is issued.
The exact date of the debit is then written on the bottom of the invoice.
Only if there is something about "transfer the invoice amount to us" with a bank account (Vodafone... IBAN... BIC... reference...) do you have to transfer it yourself.