Bad service

I’m currently experiencing bad customer service from Astron energy Lyttelton Manor. I filled up petrol in June with company money. I need to submit a claim for that fuel but my invoice has faded. I asked a lady called Natasha to assist. The lady says I cannot be assisted cos they throw away the invoices of previous months. I’m currently frustrated because my salary will be deducted. When I tried calling the customer care centre my calls get dropped. I need urgent assistance.