Repair corrupted m4a AAC file

We recorded two hours of a podcast via Skype but, although it saved, the file is unplayable. I've tried to open it on Media Player, VLC, Audacity and Premiere Pro and it won't work. My guess is it is corrupted and I understand that it is possible to repair a corrupted audio file but I don't know how.

If the price I've suggested below is unfair for this kind of work, please let me know.