Bad customer service

The way I love vodacom they never dissapointed me like this, I have ordered an iPhone, it came with a battery problem, they requested me to return it and the return process was fast, I was told that they are giving me the new device, only to find out that they will be doing another application from the start, now I receive the other one, this one without even going further to use the speaker is very bad both on phone call and when trying to play music, the speaker is having this irritating sound that if it was old phone one would say is a dust, I called vodacom to notify them, I ask if I can come to vodacom head office in person to exchange because this thing of up and down with return of faulty device is not on, I can't apply for the third time this is a negative impact to my profile, the consultant is telling me that there is no any other option than to return and re-apply, she said there is no exchange, how can they don't have option to exchange, I didn't want to complain here but I also don't have choice since vodacom is not helping me, how can they can't exchange? I can't pay for something that am not happy and this is dissapointing because I need phone so badly💔