No quality Guarantee on Job done.

Booked in phone under warranty for repairs as it wasnt switching on past the intro. Checked online and appears to be common issue tried rebooting to factory settings. didnt work.. Phone was checked for water damage etc in the store prior to being sent to service centre.Phone replaced with new motherboard. In about a month phone has same problem, now out of warranty. Not switching on past the intro. . Took it back and very cold customer service agent seemed to imply that didnt bring it back in time. Phone not checked for water damage but checked for scratches. Called the call centre, blind transfered to the store. Called back call centre agent was very defensive. Does Samsung not guarantee the job they do? Inconsistent checks from rep to rep when booking phones. Now I am being accused of dropping the phone thats why its not switching on and I am forced to pay for the same thing they repaired. The issue is not the money but the inconsistent approach and customer effort. Have replaced my phone with an iphone and will not be buying Samsung again. In the interim would like this resolved. Appears to be third party repair centre is Samsung Korea aware of sub- standard servicing?