replacement damaged phone

I took in my damaged phone back in January but I was told the phone is faced out and they gave you another phone which was a used phones and had to pay access fee of R300 for it and only to find that the phone is not working properly it kept rebooting itself whenever I use the Internet OR trying to download a new app and I took it to polokwane repair centre and they forwarded it to the repair centre and I was told the phone is fixed on 3 occasions and I was told that the phone has no faults and I feel like stupid now and I tried explaining to the call center agent disappointly she couldn't be of any help and I asked them to replace these phone as it is insured but I cant get help so Vodacom has failed me and I can never recommend it to my family or friends so what do I do?i have send an email to escalation department but no respond what so ever