EG95-EX, GPIO 39 as Input

I would like to use GPIO39 on EG95-EX as an Input. It looks like that this pin is configured by the UART and therefore an Output (Ring Indicator). When I measure voltage, this pin is stuck at 1.8V. When I try to reconfigure the pin using as an Input using: AT+QGPIOS=39,0,0,0,0 it still outputs 1.8V. When pulling the voltage down the voltage immediatly goes up again to 1.8V, therefore I assume it is hard driven and not leakage.

How can I configure this pin to be an input?

Thanks
Martin

Is it necessary to change GPIO39 from output mode to input mode?
The GPIO number of RI is 75.

Execute command:AT+QGPIOS=39,0,0,0,0 Configure as an input pin
Pull it low externally and execute the instruction AT+QGPIOR, if it is read as 0, it proves that the configuration is successful.

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