Billed for data not used

On the 3rd of May 2015 I got a bill of R 3 331.08 on a data contract of R 179.01 p/m. I lodged a few complaints because the date they said I used the data was dates that I wasn't even home to use the data, and each time they said they will do an investigation and come back to me with never happens. I got a SMS that said they will give me a once of discount what never happened, and when I phoned to ask about it they didn't know anything about it. <br> I paid an amount of R 953.90 because a lady phoned me and said If I pay the months amount and the total vat they will activate the data card and look into it, but that never happened.<br> All of this is giving me a bad credit record, can someone please come back to me regarding this.