Use
mobi2mobi to change your title. You can also change the author. I haven't tried it directly on an AZW file (the Amazon file extension) but since it's a flavor of MOBI you can temporarily change the AZW extension to MOBI if need be to run mobi2mobi. Then just change it back to AZW before loading it on the Kindle.
In the same subforum there is GUI, that I haven't tried, that would make it easier to run mobi2mobi.
HTH