Is one circuit connected to two breakers safe?
Did the electrician replaced the Service panel only, or (s)he also worked on other things like adding junction boxes and ran new conduits? The problem of 2 breakers (let's call #1 and #7 connected to the same circuit (lights in this case) might not be at the Service panel, but it could be that he had mistakenly connected wire from #7  to the existing light circuit which already had been connected to #1 prior to this, at the new junction box. You need to trace down where the old lighting circuit connected to those #1 and #7 wires.