udev rule (file /etc/udev/rules.d/modem.rules):

SUBSYSTEM=="tty", ATTRS{idVendor}=="12d1", ATTRS{idProduct}=="1001", SYMLINK+="modem_huawei_$env{ID_USB_INTERFACE_NUM}"

Ensuite, il faut prendre en compte le changement

sudo udevadm trigger

~/.gammurc

[gammu]

port = /dev/modem_huawei_00
model = 
connection = at19200
synchronizetime = yes
logfile =
pin = 115200 
logformat = nothing
use_locking = 
gammuloc = 

/etc/gammu-smsdrc

# Configuration file for Gammu SMS Daemon

# Gammu library configuration, see gammurc(5)
[gammu]
# Please configure this!
port = /dev/modem0 
connection = at19200
# Debugging
#logformat = textall

# SMSD configuration, see gammu-smsdrc(5)
[smsd]
service = files
pin = 115200
logfile = syslog
# Increase for debugging information
debuglevel = 0

# Paths where messages are stored
inboxpath = /var/spool/gammu/inbox/
outboxpath = /var/spool/gammu/outbox/
sentsmspath = /var/spool/gammu/sent/
errorsmspath = /var/spool/gammu/error/
RunOnReceive = run_on_sms.sh

Fichier /etc/systemd/system/multi-user.target.wants/gammu-smsd.service

[Unit]
Description=SMS daemon for Gammu
Documentation=man:gammu-smsd(1)
After=mysql.service postgresql.service network-online.target

[Service]
EnvironmentFile=-/etc/default/gammu-smsd
# Run daemon as root user
#ExecStart=/usr/bin/gammu-smsd --pid=/var/run/gammu-smsd.pid --daemon
# Run daemon as non-root user (set user/group in /etc/sysconfig/gammu-smsd)
ExecStart=/usr/bin/gammu-smsd --user=${GAMMU_USER} --group=${GAMMU_GROUP} --pid=/var/run/gammu-smsd.pid$
ExecReload=/bin/kill -HUP $MAINPID
ExecStopPost=/bin/rm -f /var/run/gammu-smsd.pid
Type=forking
PIDFile=/var/run/gammu-smsd.pid

[Install]
WantedBy=multi-user.target