modemmanager WWAN connection problem

System: Linux X200 2.6.32-22-generic #33-Ubuntu SMP x86_64 GNU/Linux
Package: modemmanager
Package-Version: 0.3-0ubuntu2

When I try to connect to my WWAN service provider (with a "Ericsson F3507g Mobile Broadband Module" in a "Lenovo X200" Laptop), I get the following error messages (/var/log/syslog):

May 19 16:13:35 X200 NetworkManager: <info> Activation (usb0) starting connection 'A1/Telekom Austria A1 Breitband'
May 19 16:13:35 X200 NetworkManager: <info> (usb0): device state change: 3 -> 4 (reason 0)
May 19 16:13:35 X200 NetworkManager: <info> Activation (usb0) Stage 1 of 5 (Device Prepare) scheduled...
May 19 16:13:35 X200 NetworkManager: <info> Activation (usb0) Stage 1 of 5 (Device Prepare) started...
May 19 16:13:35 X200 NetworkManager: <info> Activation (usb0) Stage 1 of 5 (Device Prepare) complete.
May 19 16:13:35 X200 modem-manager: (ttyACM0) opening serial device...
May 19 16:13:35 X200 modem-manager: Modem /org/freedesktop/ModemManager/Modems/1: state changed (disabled -> enabling)
May 19 16:13:35 X200 modem-manager: Got failure code 100: Unknown error
May 19 16:13:35 X200 modem-manager: Invalid error code
May 19 16:13:35 X200 modem-manager: Got failure code 100: Unknown error
May 19 16:13:35 X200 modem-manager: Modem /org/freedesktop/ModemManager/Modems/1: state changed (enabling -> enabled)
May 19 16:13:36 X200 modem-manager: Registration state changed: 4
May 19 16:13:41 X200 modem-manager: Registration state changed: 1
May 19 16:13:41 X200 modem-manager: Modem /org/freedesktop/ModemManager/Modems/1: state changed (enabled -> registered)
May 19 16:13:42 X200 modem-manager: Modem /org/freedesktop/ModemManager/Modems/1: state changed (registered -> connecting)
May 19 16:13:44 X200 modem-manager: mbm_e2nap_received, disconnected
May 19 16:14:34 X200 modem-manager: Modem /org/freedesktop/ModemManager/Modems/1: state changed (connecting -> registered)
May 19 16:14:34 X200 NetworkManager: <WARN> stage1_prepare_done(): GSM modem connection failed: (32) Busy
May 19 16:14:34 X200 NetworkManager: <info> (usb0): device state change: 4 -> 9 (reason 1)
May 19 16:14:34 X200 NetworkManager: <info> Marking connection 'A1/Telekom Austria A1 Breitband' invalid.
May 19 16:14:34 X200 NetworkManager: <info> Activation (usb0) failed.
May 19 16:14:34 X200 NetworkManager: <info> (usb0): device state change: 9 -> 3 (reason 0)
May 19 16:14:34 X200 NetworkManager: <info> (usb0): deactivating device (reason: 0).
May 19 16:14:34 X200 NetworkManager: <info> Policy set 'X200 LAN' (eth0) as default for routing and DNS.

Somebody in an Austrian forum wrote, that modemmamnager connects to the wrong device ("ttyACM0" instead of "ttyACM1").:

https://forum.ubook.at/index.php?page=Thread&threadID=1127

How could I tell the modemmanager to choose the right device?