I don't know much about this, but the commands I would run, after your phone is connected is:
lsusb
su -c 'fdisk -l'
and enter root password when promted, and provide here the output so that someone may be able to help you. Be very careful with the syntax (maybe copy and paste the above).
If you do not see the mobile phone's /dev/xxxx with fdisk, then IMHO it will be very difficult to proceed.