You can’t really be 100% certain.
Display problems are usually caused by misuse by the user e.g. dropping phone once or a lot of times even, putting it in back pocket and sitting on it, getting it wet etc or if it is a faulty replacement display (bad batch perhaps) it may be beyond the control of the repairer to know until the phone is returned as faulty again after a period of time, as it should have been tested when it was installed
A reputable repairer will give a guarantee on their workmanship which usually also covers the display if it malfunctions during the guarantee period so long as the display problem has not been caused by the user of course.
Cette réponse est-elle utile ?