How to nicely tell someone they're being a royal pain in the you know what?

There’s this friend of my bf’s who calls him constantly. Well every other day. You can set your watch by him, he’s so predictable.

First he always calls the landline. Not once, but at least five times before finally calling his cell phone. We usually don’t answer the landline because that’s mostly telemarketers.

My bf’s too nice for his own good to tell this guy off. He tells me he’s getting fed up with him calling all the time but doesn’t quite know how to say it to him.