Damaged product - no refund - no return

I bought a Robari ****eater at Game in Dec 2015. I used it twice in early 2016. At the 2nd use I notice the cutting wire is very short and since I could not figure out the manual to change it, I took it to the STIHL lawnmower shop in S/West to aks them to help me do it. They took one look at the machine and said I should return it since the motor seems to be loose and the whole shaft is turning. I returned it a few days after the 30 day return-for-cash clause. They would not give me my money back and said they would send it off for repairs. I pointed out that clearly the machine is a dud and can it be fixed? I was told that they would contact me when it comes back, that it would take 2 weeks. They took my name, telephone number and a copy of the till slip. it is now March, 17th, 2016 and I have not heard one word from them. In the interim I have read on the back of the till slip that should I not be contacted within the specified period, the refund will be paid out to me. I phoned them but they say no, this is not true, they do not pay the refund after so many months. What do I do now? I would like my money back since I don't have a machine, it was a dud anyway.