Cell phone repairs

I renewed my contract with MTN in June 2015 and got a new Sony M4 Aqua, on the 30th of October I handed my phone in at the Volksrust branch to be repaired and I was told that it would take about 3 weeks to fix witch was strange because my friends phone had the exact same problem as mine and he got his phone back within 3 days ( DIFFERENT SUPPLIER THO ) It is now almost 10 weeks later and I still don't have my phone back, they keep on telling me they are waiting for spares..... How long do I still have to wait???