Mtn bad service

I am contracted to MTN, I took a phone Sony Experia X ultra, so the phone battery started giving me a problem in Sunday afternoon 19/05/2019. So on Monday 20/05/2019 I too it to MTN in Pan Africa Mall Branch so that they can have a look at it so I signed the necessary documentation and I left the phone with them. Because I didn't receive any form of communication from MTN I then decided to go to the branch and get feedback. So on Wednesday 22/05/2019 I went there when I got there they told me the phone is still at the store and they have no idea when the courier company will come and collect it. On Friday 24/05/2019 I went there again and again my phone was still at MTN and they were still awaiting for the courier company to come and collect it. I just had to take my phone back, bcz I felt they were just *********** and they didn't even care about me as a paying customer. Firstly they don't come up with solutions they just tell me problems they having.