Done be quick to pick up the phone when H calls. When you do finally answer a hour or two later, tell him You were busy doing "X". Then see what he wants. Do stay on the phone long, and try to end the conversation and end the call first.
We made a deal when H moved out that we would always answer the phone when the other called, in case it was something that involved the children. I have ended every one of our phone conversations first - usually he pauses for a long time and I just say goodbye. In two of the last three phone calls I said goodbye, he said wait and either told me a story about the kids or told me his schedule (which could have been done in email) and then paused and I said goodbye again and hung up.
