New Contract and Two Broken Devices

Hi <br> <br> I have just renewed my contract with Vodacom and I received a new Nokia 830 <br> 2 days after having it the screen started lifting ,I took it back to Vodacom and they gave me a new device because it was within the 7 day period. The second device also had a collapsed power button and lifting screen, i returned this device to Vodacom and ask if the could change device because clearly there is something wrong the Nokia 830s the have in stock. Vodacom said this is not is not possible and i have to keep taking the phone in for them to send it off and replace or repair. Vodacom said they cannot give me i different model or brand of phone, my contract is less then a week old. I am now paying for a new device which i have yet to own for more than one day! This is totally unacceptable I do not want to accept a third Nokia which may break 1 day after the 7 day period and then i will have to live 24 months with a broken phone, I will be cancelling my debit order with Vodacom until this matter is resolved and Vodacom lets me choose a different device for the same value as the Nokia 830. Very disappointed with the Nokia 830 and i think Vodacom have a defective batch. Myles