CentOS - May 2015 - CentOS 7 and mobile broadband Ericsson F5521gw

Hello all,

I have got problems to get my mobile broadband connection running on my Lenovo
T420. But NetworkManager doesn't seem to connect. I ran through the wizard
for mobile broadband connections but it doesn't work.
The Ericsson f5521gw seems to run with cdc_ndm module.

I also installed modem-manager-gui and unlocked my sim by using mmcli. But still
NetworkManager can't establish a connection. I also can't delete
connection out of the NM-GUI so I needed to remove them from
/etc/NetworkManager/system-connections. Did I miss something? The logs seem to
be fine so far. My CentOS 7 has all recent updates applied.

Thanks in advance
Tim