Thank you for your reply!
I bought my phone online from T-mobile (telecomprovider). First I made a phone call to T-mobile to explain the problem and I had to send it to them. They have an external repair service called 'Dynafix' and it's not the best repair service, they have a bad reputation.
After 2 weeks I received my phone and it was unrepaired and the explanation that was given: 'We looked very deeply into your phone, but we couldn't find the problem'. So the second time I went to the T-mobile store and there I explained the problem with the second microphone. The staff member said that she would send it back again for repair to their external repair service with a better description of the problem.
So after 2 weeks again I received an unrepaired phone again with the same description. So I proposed to make a handsfree phone call or voice memo with the staff member also listening, but she said that it doesn't matter if she listens and sees the problem by herself... The only thing she could do was send it back again for repair. That was really frustrating, you would expect that they could give me a better solution if they would see the problem by themselves.
So I thought it would be better to send it to Microsoft this time, but it was the same story. Again I received an unrepaired phone yesterday... I made a phone call to their repair point an they said that maybe they would give me a new one if I send it back again for repair 2 more times. And that's good news but i'm a little bit tired of this situation, I'm for waiting 6 weeks now and still nothing.
It really isn't that hard to understand the problem and I really don't know why they don't fix it:( All I'm asking is to fix the second microphone. We also don't have microsoft points in the Netherlands an the repair service is too far away.
The next time I will give an easier explaination like you said and I hope that they could give me a new phone if they would again fail to repair it.
btw. sorry for the long reply but now you know the whole story;)