Can the planiffs lawyer be a process server in a divorce case in Georgia?

It would be hard to proceed against the lawyer for anything. You were technically not served because as you said he's not a process server - its not like he was pretending to be one. You were provided notice that a complaint was filed against you and anyone can provide you notice of a complaint. Had you not shown up to the hearing, they would have likely been ordered by the judge to hire a process server to officially serve you. But you showed up to the hearing. At the hearing you should have complained to the judge and the judge would have likely scolded the attorney as this is a common practice amongst small law firms, it is not the proper way to do things.  This post is not legal advice and no attorney client relationship has been created. You are always best advised to present these facts to an attorney who can then best advise you as to your potential claims.