Hi mehd1952: Does the ATD command not work? It is, in essence, a voice call so I would expect to use these commands:
ATD*21*094#; (don't forget the semicolon)
ATS6=n (n is a delay in seconds range 0 to 999)
ATH (Drop call)
you will have to experiment a bit with the delay or you may want to insert commas in the dial string and use ATS8=<n> to set the default delay for a comma. I have attached the latest AT Command set document to help
The ATD0917xxxxxxx; dose work but ATD*21*xxx...#; doesn't .
I read Sim900 AT_Command manual V1.03 but I can't understand ATS6=<n> what does it do exactly? is it necessary? I just used ATS6=1
what should I do now?
Try the following:
ATS8=<n>. This will set the default delay that is inserted by a comma
ATD*21*,094#,;
ATH
--if you were doing this from a handset you would dial the service code, wait for a resonse, dial the number for forwarding followed by # then wait for acknowledgement before hanging up. You may need to experiment with the delay value or just add more commas
ATS6 adds a delay between sending an ATD and the module actually dialling, so this is probably not right for you