Default [Q] Karbonn Titanium s5 isn't recognising sim

Hello, I have a Karbonn Titanium s5 which is failing to recognise sim cards. When I slot in any sim, nothing shows up indicating that there's a sim inside. When I try to dial a number it also tells me to turn off airplane mode even though airplane mode is off. Is there a way of installing a fresh OS in the phone using a computer? I can't perform the OS installation through the phone because it won't connect to the internet. Or is there anyone who has faced a similar problem and who can help me out? I'm stuck! I'm running Android v4.1.2. HELP!!!!