ZAP Trunk Long Distance Dialing Rules

Hello,

I am new to this, and I am trying to set up a VoIP phone system. I am able to make inbound and outbound calls very well, but when I try to make long distance calls I get a busy signal. I would like to know if there are any suggestions pertaining to my dialing rules listed below.

1757+NXXNXXX
1+NXXNXXNXXX

Is there anything I need to add to this? Thank you for your help.

If anybody has anything that would help, maybe a site to go to, that would be a great help. Thank you.