Poor service delivery

Afternoon my name is Muzi I've took my iPhone 6 for repair it had a problem it wasn't charging and it wasn't switching on I was so suppose to switch it on using the charger but still it use to switch off while it was on the charger and this happened after It came back from repair again cause it had a problem with battery, so I took it back again for repair and they brough it back cause find my iPhone was on, so I had to switch off and book it again and took a month then they told me that they couldn't fix it they have sent it to the expects at their Head office but it is not yet back I don't know what's happening and I have a good mind of not taking it back cause I can't keep on repairing the phone it loses value