GSM modem BGS5-T2M (SEA Prague) does not support the command AT^SSMSS=1. This is part of the definition for the Siemens TC35i modem type in the alarm SMS configuration. Therefore, when using this type of modem, it is necessary to select another profile, ie Wavecom or General, which have an initialization sequence
ATE0\r\n
AT+CPIN?\r\n
AT+CNMI=0,0,0,0,0\r\n
AT+CMGF=1\r\n
AT+CPMS=\"SM\"\r\n
Also note the need to enter the phone number in quotation marks, see "00420731585458".