typedef struct tagRILDevSpecificParams {
        DWORD dwFunctionID;
        BYTE *lpInputParameters;
        BYTE *lpOutputParameters;
} RIL_DEVSPECIFIC_PARAMS, *lpRIL_DEVSPECIFIC_PARAMS;

And I've tried to convert this to:

[StructLayout(LayoutKind.Sequential)]
        public struct RIL_DEVSPECIFIC_PARAMS
        {
            [MarshalAs(UnmanagedType.I4)]    
                public Int32 dwFunctionID;
            [MarshalAs(UnmanagedType.ByValArray)]
                public byte[] lpInputParameters;
            [MarshalAs(UnmanagedType.ByValArray)]
                public byte[] lpOutputParameters;
        }