Enter the dial up area code and phone number. The area code here and in the Dial settings window must match.

If the customer must dial the local number with the area code but no "1," make sure the area code here and in the Dial settings window match, and then insert the area code before the 7-digit number in the "Telephone number" field.

"Disconnect if idle for more than ..." and "Minimize connection status window" should be unchecked and "Enable dial on demand" should be checked (unlike the examples here).

"Bring up a terminal window after dialing" can be checked if the customer is having trouble connecting.  See the Answerbook solution, "Win31 - Unable to negotiate dial in connection (failed)."