Problamatic repairs

I had a problem with my phone screen and took it to the walk in centre where I was told it would take a week to repair. I took my phone in on the 13th of January 2016 and phoned again on the 23 of January to hear if the phone was fixed. They told me the phone was replaced but failed quality assesment. Up to date the 3rd of March I still don't have a phone and every time I phone they tell me thy will escalate the matter, I must have heard this about 15-20 times while no-one can answer me on where my phone is. Every time I phone Im told that it would be sorted out within the week I should phone later in the week again but nothing came of it.