You can do a full factory reset, but if your current alarm company has the Installer Lockout feature enabled it prevents the panel from resetting the installer code to the factory default. That is why people are saying you may need to change the panel. If you have full LCD keypads re-programming really isn't that big of a deal.
I have been running a DSC 1832 panel for the last three years with Internet only using an Envisalink module . Their monitoring is something like $12 a month (Canadian). Works great.