Complain about the car I bought

I bot a very nice BMW 2 series with buy cars Midstream, test drive was like 60seconds, after two weeks the car started making a lot of terrible noise. When I sent n email to we buy cars to lay a complain I got a call and feedback on email saying I can either bring in the car which might take them long to fix or I can fix with RMI Mechanic which I did. We buy cars asked me to send the tax invoice, pop n proof of banking details, today after I send numerous emails enquiring the refund they are telling me "SORRY BUT YOU SIGNED THE Contract" They knew I signed the contract b4 they advised me to fix the car and send back the tax invoice. They ignored the damaged parts which I had to buy to fix car. My colleagues were so impressed when I sold the car, bcoz we buy cars came to the my work premises. I can't wait to warn them not to buy the car from we buy cars coz some of them asked me about the process n did the enquiry with we buy cars so she an change the car.