Deviation between invoice and contract amounts

[Attila5]

Hi, I am home Internet customer and decided to hire mobile line with vodafone. I was informed that I would have combo 10 EUR discount per month, 20% off (promotion) and no installation cost. The contract sent to my email shows exactly this, with a montly amount of 13,99 EUR for my "GigaMobil XS ohne Smartphone 24 Monate Mindestlaufzeit". My first invoice was 26,39 EUR. Could you please help me understand the deviation and explin way I was informed that the monthly amount would be 13,99 EUR?

[Mav1976]

Hi @Attila5,

Can you upload a copy of your invoice but without personal data (name, address etc.). 

I assume that you overlooked the pro rata for this accounting period and the full rata for the next accounting period at your invoice.