Charger replacement

I upgraded to the Sony Xperia Z5 and received my phone 17/12/2015. Now the charger does not wanna work. Went to the store in Cape Town, Golden ACre, and was told by the regional manager that I would have to book the phone in together with the chager. The both of us plus a consultant checked the phone out individualy and it was determined that it is the charger and not the phone as the phone works with other chargers. Why would I now have to be without my phone, that I am paying for for a full full month, for up to 21 working days. All I want is for the charger to be replaced. Please call me tomorrow 13/01/2016 as I am not available today.