Damaged drill bought but it's not their problem

I bought a Skill drill from Builders for a car port roof I was putting up and the weekend I started using the drill and found a bad smell, later I discovered the smell was from smoke coming for the drill. I took the drill back to Builders where it was tested and according to them there was no problem but the person assisting me also advised me that if there is a problem I should wait for the drill to completely break before I returned it as they will then have to assist me in a repair of replacement. a couple of weekends later the drill stopped working and I returned it to Builders in a week they let me know I can come and collect the drill which I did, firstly they could not find the paper work so I decided to open the box and found the drill disassembled back in the box with no explanation. a couple of weeks have passed now and they told me the drill is burnt out and not there problem I must talk to the people from skill, they gave me a number and a name to talk to but the number just rings I called builders to confirm the number and explain it is not working they did confirm and said the number works. Builders is sending me on a run around till I get tired and just let it go!