Used usb to serial converter and its 5V supply to M590 board(Chinease) it has a diode in series to drop the voltage from 5 volts to 5-0.7=4.3 Volts or less

Neoway M590 worked fine to send SMS with
AT
AT+CMGF=1
AT+CSCS=”GSM”
AT+CMGS=”+9198xxxxxxxx”
“test messege ”

Also checked USSD working without any problem tested with
ATDT*123*1#;

Calling works with
ATDT;