Personal Info given out

I had a faulty phone sent to Cell C Repairs before getting a new one so they could check that I hadn't done anything wrong to the phone. I was very pleased to have received a new phone but then I started getting calls from a gentleman who was asking me for my I Cloud login details so he could clear the phone that Cell C sold him. He also said that he had 3 phones all together from Cell C, none of which were cleared and he confirmed with us that he did not work for Cell C in any way. So my phone was sold to a complete stranger with ALL my infomation, photos, Gmail, Facebook etc etc on it. This is completely unacceptable, I had photos of my 3 girls on this phone and I dont know this man from a bar of soap, I am absolutely fuming!!! This is an enfringement of my privacy!!! This man actually found my work contact number in my emails so he went through my emails and at one stage even changed my passwords so I was unable to log into my OWN emails. I have tried emailing ppl at Cell C, I have been in store and I have spoken to the supervisor at the repairs who told me that it was someone from Cell C asking, which is a lie as i have copies of the whatsapp conversation with the guy that bought the phone saying he has nothing to do with Cell C. I told him that was not a good enough answer and I am still waiting for him to call me back. I have given Cell C more than enough time to come to me with a solution to this problem. I will be taking this further if i do not hear from someone.