bought a new phone :microsoft lumia 430

On the 25/07/2015 was a Saturday my mother in law Miss Veronica Motaung bought a cell phone from Edgars Eyethu mall in Orange Farm. When the consultant was busy with her he told her that the phone has a guarantee and a warranty if something is faulty with the phone she would have to bring it before 7 days,On the 30/07/2015 Thursday(its still within the 7 days grace period) she sent her son to take the phone back and he was told that its a network problem as the phone needs to take 2 sim cards he must just keep trying switching the phone on and off, we have been trying to put the 2 sim cards as it allows 2 sim cards but it does not read the second sim.On the 02/08/2015 she went back to take the phone back the same person said you need to put 2 mtn simcards and she did the phone still didn't work after she went outside to check for network. She was told that the phone will be taken in for repairs and she would receive it after 7 days she accepted. After this guy finished with the forms he then told her that she will get it after 4 weeks and she must come and check no one will call her. Can someone please call her on *** to have this matter sorted as soon as possible.