If corporations can't lobby, how can they get laws that are fair to them?

Revoking corporate personhood would not immediately prevent corporations from lobbying, but it would allow laws to be passed (and enforced) that would restrict corporate lobbying and campaign contributions. If a state legislature or Congress is considering legislation  that affects a particular industry they would be able to hold hearings and interrogate corporate representatives. If a corporation feels its needs a change in the laws, not for its own profits but in order to insure competition or public safety, it could petition the legislature to hold such a hearing.