Incoming SMS with diacritic

Hello, I have a problem with incoming SMS (only those with diacritics, in Czech). All incoming SMS messages are displayed as Chinese or Japanese symbols.

As Gateway im using GAMMU.

Sended message: Zkouška příchozí SMS.
Recieved message: 婫潵얡歡⁰얙쎭捨潺쎭⁓䵓

Can anyone help? Many thanks.