Hi!
You mean – first digits of the dialed number can’t be 0 ? Or the user will dial only 1 digits and this digits can’t be 0 ?
You can use “manipulation” and simple change first 0 to any other digits or number.
But you can’t create situation when after dialing 0 user will get Fast Busy Tone and then ATA immideatelly return to Dial Tone for continue dialling.