I don't see how one would use "samtale" when talking about appointments. As londoncalling pointed out, "samtale" means "conversation".
This sentence literally means "Do you have a time." In this context, though, it means appointment.
Example: If I had a dentist appointment, I might say: "Jeg har en tid ved tandlægen klokken 3."
It is just as correct but when we, as we most often do, speak informally we just say "jeg har en tid ved lægen" instead of "jeg har en aftale med lægen" - actually as i just said that to myself it was clear that we would probably never use the latter, even though as i said in the begginning it is just as correct.