When it’s not enough to just read and write files on a VFAT file system there’s a good change
mtools can help. The only problem is that
mtools work with drive letters. To assign a letter to your device you need to edit
/etc/mtools.conf. This is the line I use to access the VFAT partition on my USB stick:
drive d: file="/dev/sdb1"
After this I can use
mlabel to set the label of the partition: