Hello! 
I had a tariff plan for Ukrainians (MagentaMobil Prepaid Ukraine), but after receiving a German residence permit, I’ve changed my tariff plan to MagentaMobil XL Young Flex. In Telekom Shop on 26th of September an assistant told me that the first month of using of this tariff plan will be free. But now I’ve received an invoice that told that I need to pay 10,83 euro for September. Is it okay, and I simply haven’t understood something when changed my tariff plan, or it’s a mistake? 

Thank you for your help!