Student or Learner
If I am talking on the phone and then ask the caller to hold the line as I have to attend to something urgent, which is the correct apology when I get back to him/her on the phone?
1. I am sorry to keep you waiting.
2. I am sorry to have kept you waiting.
You will hear both from native speakers.
2 is more grammatical, but who cares? It's the apology that matters.