Ebucks double points not given

Good day

I would like to complain about the ebucks not been rewarded to me for my double points of only filling up at engen.i have take out my car loan with fnb and was expecting this ebucks.yesterday I called in and there was a agent who assisted me but advised me that there was one amount that was showing that I purchased fuel at another service station which I have never. He provided me with the date in which I contacted the service station.they had provided me with a slip on that specific amount I went to the car wash add naught in the shop.when they provide the slip they say the teller put cash and fuel into my slip.i spoke to the manager there and they are willing to write a letter to indicate that it was not fuel purchased at the station. So if I had not picked this up I would have not known I have never filled up fuel at any other station and if you look at my amounts for fuel it is always a full tank. Please can this be resolved