Poor Service

I currently have a contract with MTN, I took a phone (Sony Experia) and on Monday I took it to MTN Pan Africa Mall because it was giving me problems with a battery. MTN did not communicate with me regards to the status of the progress with the phone, so On Wednesday I took an initiative to go back to MTN and ask for the feedback, instead when I got there they told me the phone is still in the store because people from Sony didn't send the courier company to fetch it. I do not understand why the consultants do not communicate with the customers about such things instead we as the customers we have to always go to the store and ask for feedback whereas it is the consultants duty to always inform the customers about the status/progress of the query. now they told me it will take about 7-14 days, for the phone to be fixed, how will that be possible if the phone is still in the store!!!!! we cant be paying for phones that are still in the store shelves, that is just ridiculous, kindly advise a way forward to the matter in question.