Challenging false narratives

I am helping someone with a PIP appeal,I have raised that the assessor has mis interpreted the assessement but they have doubled down and fabricated a second telephone interaction.
Is there an opportunity to request the audio recordings before tribunal as they have ignored the request for the assessment - is there a document disclosure stage? .
I was with the person on the assessement but did not realise that fabricating them was common and there is no recording of it

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