NetworkManager doesn't connect to Mobile Broadband

I have an HSDPA USB Stick modem model E1550, detected by lsusb as follows:
ID 12d1:1001 Huawei Technologies Co., Ltd. E169/E620/E800 HSDPA Modem.
I add a new Mobile Broadband connection in KDE Network Manager Settings, it correctly finds the modem and allows me to select my country and operator (Russia Beeline). I select default APN, which is home.beeline.ru (though I've also tried internet.beeline.ru as is told on their website), then say Finish.
Dial number, username and password are correctly detected. I select PIN as "Not required". Now I press OK in the dialog appeared, and try connecting from plasma network-manager widget, and... nothing happens. Seemingly.
I get this output in /var/log/syslog:
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Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> Activation (ttyUSB0) starting connection 'Beeline - 3G modem'
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> (ttyUSB0): device state change: disconnected -> prepare (reason 'none') [30 40 0]
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) scheduled...
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) started...
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> (ttyUSB0): device state change: prepare -> need-auth (reason 'none') [40 60 0]
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) complete.
Mar 8 01:28:51 integral1 modem-manager[9075]: <info> Modem /org/freedesktop/ModemManager/Modems/5: state changed (connected -> disconnecting)
Mar 8 01:28:51 integral1 modem-manager[9075]: <info> Modem /org/freedesktop/ModemManager/Modems/5: state changed (disconnecting -> connected)
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> disconnect failed: (32) The serial port is not open.
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) scheduled...
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) started...
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> (ttyUSB0): device state change: need-auth -> prepare (reason 'none') [60 40 0]
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> Activation (ttyUSB0) Stage 1 of 5 (Device Prepare) complete.
Mar 8 01:28:51 integral1 NetworkManager[9077]: <warn> GSM connection failed: (32) Sending command failed: device is not enabled
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> (ttyUSB0): device state change: prepare -> failed (reason 'unknown') [40 120 1]
Mar 8 01:28:51 integral1 modem-manager[9075]: <info> Modem /org/freedesktop/ModemManager/Modems/5: state changed (connected -> disconnecting)
Mar 8 01:28:51 integral1 modem-manager[9075]: <info> Modem /org/freedesktop/ModemManager/Modems/5: state changed (disconnecting -> connected)
Mar 8 01:28:51 integral1 NetworkManager[9077]: <warn> Activation (ttyUSB0) failed.
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> disconnect failed: (32) The serial port is not open.
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> (ttyUSB0): device state change: failed -> disconnected (reason 'none') [120 30 0]
Mar 8 01:28:51 integral1 NetworkManager[9077]: <info> (ttyUSB0): deactivating device (reason 'none') [0]
Mar 8 01:28:51 integral1 NetworkManager[9077]: nm_system_iface_flush_routes: assertion `ifindex > 0' failed
Mar 8 01:28:51 integral1 NetworkManager[9077]: nm_system_iface_flush_addresses: assertion `ifindex > 0' failed

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I've tried changing various settings, but NetworkManager didn't manage to connect.
OK, I've gone another way: using wvdial. Here's config which I used:
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[Dialer Defaults]
Init1 = ATZ
Init2 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
Modem Type = Analog Modem
Phone = *99#
ISDN = 0
Username = beeline
Init1 = ATZ
Password = beeline
Modem = /dev/ttyUSB0
Baud = 9600
Stupid mode = 1
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And, it worked! So, basically NetworkManager was unable to connect while wvdial connected almost immediately.
Notice that maybe the fact that I didn't have to enter APN might have done the thing, but I don't know how that should be done in NetworkManager.