Varying phone levels can be evened out to some degree using compressors in FCP or Soundtrack Pro. I find the Sound track pro interface to be confusing and very unintuitive. Your experience may be different.
There's also the simple but effective gain change tool in FCP. Choose waveform display and the graphical automation adjustment mode. Then, using the pen tool, (not the standard pointer) click on either side of a section you want to change within those two dots, make two more and drag the audio up or down as needed.
I usually raise the entire volume a bit, reduce outburst that will be too loud and then follow it with a FCP compressor or limiter. Be sure to pay attention to the master output level. It'll tell you if you need to raise or lower anything.
Reversing phone EQ is tough. Phone EQ is usually peaked at 3kHz with everything above and below rolled off. You can try adding frequencies below and above that, but if there isn't anything there, at some point, all you'll get is noise. Try it and see. Don't expect one setting to improve all phone calls. To get the best results, you'll have to tinker around a bit. Don't go below 80 Hz and probably not above 10 kHz. The human voice frequencies are mostly between 100 Hz and 6 kHz.
I have a telephone recording of an interview. It's really really crunchy; I think the recorder I used had some major auto-gain going on.
Basically, the waveforms are very full and blocky.
What filter in Final Cut Pro can I apply to try to restore it to mostly voice and less distortion?