Incorrect additional charges

On Invoice Number H0-17ZW dated 01/03/2016, there are additional charges of R 80.82 + vat = R 92.13 On Invoice Number H0-4D1C dated 01/04/2016, there are additional charges of R 30.61 + vat = R 34.90 Vodacom emailed me a list of additional charges from 29 Feb 2016 to 29 Feb 2016 As per Vodacom's list the additional charges come to R 80.81 excl vat ( 3.99 + 0.73 + 46.79 + 0.87 + 26.64 + 1.79 ) This R 80.81 was included on the Invoice HO-172W dated 01/03/2016, -> so why was I charged an additional R 30.61 (excl vat) on Invoice H0-4D1C dated 01/04/2016 ??? - This needs to be Reversed.