Repair Centre Did More Harm Than Good

My Sony Z3 Compact had a faulty lens coating after less than 2 months. I took it into Vodacom and they sent it off for repaid. I was told they would have to replace the entire back cover and never thought anything about that.<br> <br> Until a couple weeks after having my device back the entire back cover that is not supposed to be removable started falling off. I was instructed to get a job number after booking it in again and they would escalate the problem. Which I did and now I hear nothing except sms's saying they repairing it again!? <br> <br> I want to know how this happened and why this does not warrant a replacement of my device? The repair centre clearly do not seal the unit properly and now I just have to accept that it may happen again or worse water gets in and then they say it was not because of the back cover!? Then what? Seriously the unit's integrity is compromised, how can this not be addressed properly by Vodacom...very upsetting.