Vodafone — wrong charges against my mobile usage (SMS)

Dear Sir/Madam,

I am subscriber of Vodafone - [protected].
In the bill for the month of January-2009 there is wrong billing against my mobile usage.They had charged double for sending the SMS on 01/01/09.When i enquired about this in vodafone store they are saying that it is fault of handset (NOKIA N73).
The same problem occured before in the month of november-2008 also but at that time i did't realise but this time i saved the message which i had send at that particular day.Message length is only of one message but in my mobile bill it is showing two messages.
Please help me to resolve this issue.

Thanks & Regards,
Rahul Pandey