Lenovo - Mobile phone stopped working in just 20 days of purchase

Hi,
I bought a Lenovo K* Note from Amazon, Date: * February ****. Order Number: ORDER # ***-*******-*******
IMEI Number: *************** / ***. Lenovo Service Invoice Number: SOIN****************
After ** days of usage of the phone. The phone started to auto-restart, heat issue, slow performance and on ** February ****. It was also not able to boot up.
I took a day off from my office on ** February ****, So that I could visit the service centre. So that I could get my mobile repaired or replaced they said in one day they will get it repaired. They failed to repair my phone stating parts are not available and extended their service due date till Monday ** February ****. They failed to full fill their promise on Monday as well. In just ** days, they are saying the motherboard of the mobile had turned bad. How the company can be built such a product that could not even last for a month. Every time, they are saying the parts are ordered but not received. They (Sathyam Electronics)(Door No *-**/*, Ground Floor, Chaitanya Chambers, Dilsukhnagar, Hyderabad - ******, Beside Airtel Office, Chaitanyapuri)
Contact Number: +**-**********
I have tried to contact Lenovo chat support much time but that was no help to me. They have made serval fake promises to me last Saturday **-February-**** and today **-February-****. I want them to replace and issue me a new phone or my money back.