bad experience

I bought a laptop at the end of January last year, but by late March, it had stopped working. I returned it to the store, and they promised to repair it. I received a call in late September stating it was ready, but by then, I had purchased a new laptop after being without one for over three months. When I requested to cancel my purchase, they took no action. Now, they are blacklisting me for not paying for a laptop I no longer have, and the manager refuses to address my situation.