Unfair practice

I bought a blower vacuum for the garden at Builders Warehouse in Woodlands. When it stopped working I got someone to take it back. He was told that because it was out of warranty, it would be sent to a company that does such repairs to check what the problem was. He signed it in. We didn't hear from them for a couple of weeks. After following up a couple of times they gave us the phone number of the company they had sent it to. The company then gave us a quotation for the repairs, over the phone and wanted a response as to whether they should go ahead and repair it or not. The person I had asked to phone the company told them he was going to consult with me and get back to them. After considering the cost of repairing the blower I decided that it was not worthwhile to repair it, but rather to buy a new one. When we contacted the company back, we were told that the blower had been repaired and we would be liable for the costs. The was no instruction from me or an indication that we were accepting the quote. The blower is now back at Builders Warehouse and I have been told that I cannot get it unless I pay for the repairs, which I had not authorised.