Buying damage phone

I bought an A3 sumsung on April this year at telkom, a month 2 weeks later the phone has the problem of restarting its self when I use 15 min or longer. I took it back they said it will be taken to repairs to check the problem. I wait a month not having phone they brought it back they say phone has been fixed. 2 days after the phone does same thing it went again to second repairs for same problem. I didn't have the phone again for the whole month the phone is back now but this does same thing. I asked Sharman store manager to give me contact details of Wynand person is dealing with this case, she told me their system can't allow her to get his number I must emailed him I did so but he rep**** he doesn't have contact details. What is that I asked him since the phone it's coming from second time repairs if does same what he will do, he told me I must record the event to get proof how can I record something when you use it restart. I am taking them to court now I will never again having contract with telkom in my life I experienced bad.