Charged for Festnetz even though I have Festnetz Flat

Hello,

I have a O2 contract with O2 flat and festnetz flat. But I have been charged for local access number when I make calls to india which were not charged for last 6 months. My accounting period is 12 of the month to 13 of next month. In this month bill I have been charged for calls made in last month.

Please can you share the email ID of customer service to contact.

Thanks,

Sunil