Hi,
it depends what is your national /local numbering plan. If you are located somewhere in Europe, where dialing long distance or local numbers is accomplished with dialing '0' and area code you may set outbound rule for numbers starting with '0' and omit zero digits (default is one digit).
If you are located in North America you can do the same with digit '1', if it is not in conflict with your internal numbers (and another rule for your local area code, i.e. 1-nnn-xxx xxxx; in this case the earlier rule should strip these four digits, i.e. '1nnn' and the next rule should allow passing of the whole number '1 nnn xxx xxxx', as dialed). It is good in this case to change the Prefix for external call (PEC) in Advanced settings | Custom parameters to '1'.
BR.