Consultant trying to prove me wrong

I have a problem with my MTN number since Jan last year. Each time people try to call me it rings once and cuts off. I have called MTN several times: consultants tell me the same thing: switch off and reboot. But this does not help at all. Today was really disappointing. I called MTN today and a girl Zukiswa took my call. She did not even try to help me by maybe refreshing my no. or settings. All she did was to prove me wrong: there is nothing wrong with your number mam, I am calling it and it is ringing. I tell her that I am looking at my phone and I am seeing no incoming call. She remains intransigent that my line is perfect and there is nothing wrong with it. Was it not fair if she had tried to investigate further? Or even try to listen to me? How can I put an effort to call MTN when there is nothing wrong my number? I got very embarrassed and ended up asking for a walk-in centre.