My handy monthly instalment is not deducting automatically.

Call the billing department on 089 78 79 79 456 to find out why the direct debit is not being used.

I am from Germany, Is that German help line number of billing department?

Yes.

Hello ​@Khan268,
in order for the monthly instalment to be deducted from your bank account, we require a valid Sepa mandate and the account must have sufficient funds. If, for example, the account does not have sufficient funds on the day of the direct debit, your bank will debit the money back and you will incur return debit charges. If this happens once, the next instalment will not be debited automatically and you will have to pay it in manually.
Kind regards, Bianca