FAILING TO RETURN A LAPTOP SENT FOR REPAIRS

I sent a laptop for repairs to Altech Autopage South Gate Shopping Mall on the 21 July 2015 (TO REPLACE THE BOTTOM COVER) which was damaged, the laptop was working perfectly only the cover were to be replaced. I submitted the documentation proofs but to my surprise I was asked to send them again and I did. I was asked to come to the shop to sign papers for insurance since It is insured of which I did on the 2nd of October 2015 BUT up until now I haven't received the laptop instead today I was requested again to sign the insurance papers and I refused. I've been sent from pillar to post by this company and they are billing for that laptop which was meant to help my child at school and I don't have it and he is struggling. PLEASE HELP