dont want to refund a tablet for cristmas

I bought my brother a AG moblie tablet for christmas on the 13th of december when i got home i wrapped it for him on christmas eve he opened it and the battery did not want to charge and when he charged it over night it only charged 70% and the battery did not last even for 5 minutes. When i took it back they said they will fix but it was still un used . I must wait 3 to 4 weaks then they can tell me if they could fix it . When i phoned head office a guy at customer care said i must just wait and they cant do anything about it. When i said im going to take it futher he said i can do what i want he does not care. And when i asked his name he hung the phone up in my ear