Can you paste the exact lines from dmesg?
drivers/usb/serial/usb-serial.c: USB Serial support registered for generic
usbcore: registered new interface driver usbserial_generic
drivers/usb/serial/usb-serial.c: USB Serial Driver core
drivers/usb/serial/usb-serial.c: USB Serial support registered for GSM modem (1-port)
option 2-1:1.0: GSM modem (1-port) converter detected
usb 2-1: GSM modem (1-port) converter now attached to ttyUSB0
usbcore: registered new interface driver option
drivers/usb/serial/option.c: USB Driver for GSM modems: v0.7.2
usb 2-1: USB disconnect, address 2
option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0
option 2-1:1.0: device disconnected
usbcore: deregistering interface driver option
drivers/usb/serial/usb-serial.c: USB Serial deregistering driver GSM modem (1-port)
usbcore: deregistering interface driver usbserial_generic
drivers/usb/serial/usb-serial.c: USB Serial deregistering driver generic
usbcore: deregistering interface driver usbserial