Vodacom Repair Centre not checking devices before releasing them

My wife upgrade last year April 2018 and received a iPhone X. Se had numerous issues with the phone. I took it to last year (July 2018) to a Voda Shop were one of the technicians said that the issues that she have are common problems on the new iPhone X and that I must book it in. At that stage she did not have a spare phone so she carried on with the phone as it is.

November 2018 she had enough of all the problems and we booked it in at Vodaworld Midrand. After about a week we received the phone back and all that they did was a Software upgrade but she still had the same issues.

Issues on iPhone X: * Struggle to connect with WiFi * Sometimes phone will be on normal DATA and she will receive no sms/Whatsapps and then all of a sudden she will receive a lot of delayed messages. * DATA usages on this phone is very high even if she is on WiFi most of the time at work and at Home. *Sometimes while she is busy on phone it will just give a black or green screen. *Sometimes like this morning she will receive Whatsapps and after a while she will receive the same messages again.

Please assist with this because she pay a lot for this Device and its not working as it should.