This is a problem why? Technically you interrupted what he was doing when you called him so he is well within his rights to say I’ll call you back.

So he should drop everything every time you call?

There's creatures who jump at your every whistle and snap, they're called dogs.

Most people would have just ignored you if they didn't want to be interrupted, he at least took time to tell you he'd call you right back. Let a guy live.

You need a new boyfriend!

One who is smart enough to know how to send nuisance calls straight to voicemail. We have the technology!

Unless it was urgent, give the poor bastard some space.

Let me guess.... You called during a crucial moment during his favorite sporting event?

I had a boyfriend like this. Any time he called (usually it was 2 or 3 in the morning) and I didn’t answer or I answered and told him I’d call him back or I couldn’t talk long, he threw a fit. Don’t be so controlling; let your boyfriend have some space.

Was he watching Netflix? Or have a DVR/TIVO?

At least he let you know instead of ignoring you