Disappointed

MTN, through their insurance broker has arranged for my phone to be fixed, but when it was returned to me, the phone had no battery. I called MTN and they confirmed that the repair centre did not receive a battery with the phone. I know for a fact that I sent it with the battery, so I called the courier company and I am still waiting for them to get back to me. I have made many calls but I have had no luck. Which leaves me without a phone now for nearly 2 months now. which begs the question, why should I be following up and asking the courier company for about my battery? They were not hired nor paid by me. Everyone is just ignoring me now and I am the one that has been inconvenienced. I need answers, do I just accept my loss and purchase a new battery? This is not fair.