Don't get any umlauts from sms

[hefee]

if I read the sms with (Huawei E270) i only the the pasts of the message that are not a umlaut.

message saved in Sim card (made sure with a mobile) "Klopuzofäblöda"

if I run: modem.sms_read(0) i'll get: "Klolpuzofblda"

without any error or any infomation, that the encoding removed parts.

if I look at the information, that is sent over the tty also the umlauts are missing. Do I need to set the encoding somewhere for the E270?