I have purchased refurbished phones from QMF befor...

I have purchased refurbished phones from QMF before and even got phones repair from QMF before, but that is all about to stop.
I purchased a refurbished Iphone 5s on the 16th November 2017 and on the 10th December it stopped receiving a mobile signal.
Sent the phone back to QMF whom assured me this would be fixed in 24 to 48 hours to which was a lie.
with countless phone calls of at least 15 to 30 minute at a time, I keep getting told (our technicians are working extremely hard to fix z problem, which is extremely annoying knowing that they are unable to find the cure to the problem.
So I rang QMF 26/01/18 to speak to a gentleman to tell him that I would like either a replacement Iphone 5s or a full refund, to be told that neither would was going to happen.
I told the gentleman on the phone that I had been with out the phone for well in excess of 6 weeks and that I'm not being unreasonable to ask for a full refund as QMF are unable to fix the phone.
But was told that a refund would take 7 to 10 business days to reach me, but my payment to them took 24 hours.
I have no desire to deal with this company again as they are extremely untrustworthy.