Dell Laptop

Bought a DeLL laptop at store on 17/12/2014. Had problems with the charger and took it back in April. Ar store charger worked again and the salesperson said it can't be replaced as the guarentee is over. Still gave problems,would switch on or off. Checked it with another Dell charger and it worked,but my one still not working. Took it back to store and they took it in with charger query,and the guarantee was still valid, on 13/06/2015. Received a call on Monday requesting password but didn't give it cause it's the charger and not the laptop. Went to store this morning and BF was told, they don't have it yet. Phoned the repairs and they said a diagnostic report was done the morning but it's the hard drive. No one contacted us whole week. Now they're saying the turn around time is 21 days. They can't just replace the charger. Phoned the store myself and they said there's nothing they can do about it and it can't be replaced. I'm not happy because they're sending us to and fro. I just want my laptop as I have work to do on it and it's work related :(