When someone asks "is there a doctor in the house?", the answer is never "well, that depends. I mean, if you're just enquiring casually then no, I'm not doing any surgery at the moment. But if you actually need a medical professional, yes, I'll become a doctor as soon as I start work."
If you phone the plumber and say to the person who answers "is that the plumber?", they're unlikely to respond "no, I did some plumbing this morning and I'll be doing some more tomorrow but right now I'm talking on the phone."