cellphone repair

It was the last week of july when i returned a cellphone which i purchased around march to the game store specifically the one in jabulani mall,when it overheated out of nowhere from there i received a message on my mothers cellphone stating that the cellphone has been received for repairs I thought everything would go well but no 2 months went by without any feedback about the repair then i wrote an email stating my concerns then i received a response saying they are sorry about the inconvenience and then i thought everything would go well but nothing then after weeks without response i wrote another email then again i received a response saying that they'll escalate the matter. So after a few days i recieved a call on my mother's cellphone from the warehouse it stated that i must pay R2100 fee for the repair but i didn't understand since the phone was under warranty when we requested a detailed report on how they got to R2100 we never got the report back its now over 4 months and I've been waiting i really don't know what to do anymore