During the first call, he pestered my work colleague to give him the contact information of an ex-colleague. My work colleague refused, partly because we don't actually have contact information for him other than a personal mobile number, which we certainly weren't going to give to someone who refused to give us a real name.
During the second call, he asked if it were possible to beam information directly into someone's brain using a laser. He informed us that he believed someone was doing this to him. My work colleague assured him it was not possible to do this without him noticing (e.g. being put inside a CAT scanner).
I answered the third call, confusing "James". He tried to ask for my work colleague but he couldn't remember his name ("Foreign chap. Maybe Eastern European." Said colleague is Dutch.) and I wasn't about to help him. He asked me if the college had any sort of device for measuring microwave radiation. Yes, I said, it does. He asked if he could borrow it or buy it from us. No, I said, you can't. Why? he asked, becoming belligerent. Because it's purpose-built and it's not for sale, I answered.
"Look, can I talk to the guy I spoke to before?" he asked.
"No, there's no one else here right now. If you leave a number and a message, I can figure out who it is and ask him to phone you back," I answered in my brightest breeziest American.
"I don't have a number," he grumbled.
"Well, that's a shame," I said.
"I'll try again later," he growled.
If he calls again, I'm going to tell him that the next transmission from the laser will erase our phone number from his brain.