There's a person whom I think is genuinely my friend. He's showed a consistent willingness to help me out and talk to me in a friendly manner, and even sometimes calls me to start a conversation. However he's pretty busy and has a heavily pregnant girlfriend. This, I assume, is the reason why he keeps getting interrupted in the middle of our phone conversations. He'll suddenly say "I need to answer this call" (on another phone) and hang up... and only sometimes call back. One time it was even "I just need to get my haircut now".
The thing is, knowing him, I wouldn't be surprised if what he was saying were true. But he's talking to me on the phone in the knowledge that, in 15 second or something, he's going to have to suddenly hang up and do something or talk to someone else. I don't really know whether to be offended or how to bring this up with him. I don't want him to think I'm demanding that he pay loads of attention to me or anything, but it is rather annoying to be in the middle of a phone call with someone only for it to be abruptly aborted, maybe to continue later or maybe not (depending on whether he remembers to call back). And then when he's hung up, it's kind of wasting my time because I'm interrupted from what I was doing and I'm making sure I'll be available for the callback that may or may not come.
How can I approach this situation and try and make communication less annoying?