Bad customer service

I bought a Lenovo laptop last year and Vangate Telkom store on contract now it's been switching off and I loose my work. When I went there they told me there is nothing they can do I can phone or email their servicing company. I did that and the company took the laptop for 2 weeks still it's doing the same thing. How can I keep on paying for the service that I can't properly use on a monthly basis as I took it back to the store and they say they don't have a solution. That is unacceptable I left their laptop with them they will see what to do as it's no use to me and they don't have a solution but they happy when they make sale but servicing their customer is very bad they do not even put effort to assist me as I asked to speak to a manager on duty regarding the laptop