Repair outstanding for one month

I bought a Lenovo a10 flex in June 2015. The unit no longer charges. I took it to the Canal Walk branch on 18 September. I have lost the invoice but was assured by the assistant that even though the have changed accounting systems they will be able to locate a copy of the invoice for me. I have given the date and amount of the purchase. I have tried to follow up instore and via phone various times and have still to today not once been able to get someone to help me. I have been without the laptop now for over a month. Can someone please tell me what I need to do to get a copy of the invoice.<br> <br> Job Card no JC***