Hi Silvana,
I believe and assume that the payment has not yet been processed.
Please raise an Invoice Correction Request(RK) for the needful..
To know more about Invoice Correction go through the link,
http://help.sap.com/saphelp_47x200/helpdata/en/dd/55fede545a11d1a7020000e829fd11/content.htm
Sriram.