"Error: incomplete setup Check Phone number" when establishing GPRS connection via IrDA

When establishing GPRS communication via IrDA and mobile (Siemens S55) error "Error: incomplete setup Check Phone number" or "PPP timeout error" are raised.
Log says that the error occurs at random place during PPP communication. IrDA
transmiters probably interfere each other, they are sending in the same time.
Solution: change script as noted bellow (`Wait for: OK`):

$$$
Send: ATZ
Send CR
Delay: 1
Send: AT+CGDCONT=1,"IP","internet"
Send CR
Wait for: OK
Send: ATD*99***1#
Delay: 1
End