When you use the present perfect continuous to say, "I have been waiting for you since morning," it does not necessarily mean that the action has not yet been completed. Often, we use this phrase when the person we have been waiting for arrives. Consequently, we wouldn't be waiting for them any longer if they are now here with us.
You may use the past continuous to denote a completed action of some duration.
"I was waiting for you for three hours before I finally gave up."
"I was waiting for you before the movie started."
"I was waiting for you when I got a call and had to leave."
You may also use the past perfect continuous: "I had been waiting for you..." but this used to indicate a continuous action in the past that was interrupted by another action. So it is followed by time phrases like:
"I had been waiting for you for three hours before I finally gave up."
"I had been waiting for you before the movie started."
"I had been waiting for you when I got a call and had to leave."
Both past continuous and past perfect continuous tenses can be used to talk about actions or situations that were in progress at a certain point of time in the past. While the past continuous merely shows continuity, the past perfect continuous tense emphasizes the duration.