iPhone 4S STK bug

Hi all,

I find the SIM toolkit proactive command "Send DTMF" is not work perfectly in iPhone4S with all iOS version. This command is workable at beginning, but if you use this command continually (about 10-15 times), iPhone 4S will return the response "Handset currently unable to process command" and without sending the DTMF.

After that this command will not work anymore (always return "Handset currently unable to process command") until you reboot iPhone4S.

This command is work perfectly in iPhone3/iPhone4/iPhone5 with all iOS, except iPhone4S.

Thanks in advance,

Joe