Damaged my laptop to prevent warranty payout?

I handed in my Acer laptop at the LetMeRepair office in George due to a power supply issue and the laptop still being under warranty with Platinum Warranty. The Laptop was inspected and the LetMeRepair team could not fix the problem and sent it to Acer. 10 days later (after I was promised delivery of my repaired device 3 days ago) I am being sent a bill for the replacement and labor cost to replace my casing as "it seems like the laptop was dropped". No repair will commence if I do not pay the fees to replace the casing. The laptop was never dropped by me and now I am still without my device having to fight this argument. Besides the damage caused I find their callcentre service appauling. I have tried to phone them on 5 occasions and never held for less than 10 minutes. Poor, poor service and poor, poor feedback!