I just looked at your listing and there is nothing to suggest that you will pick guests from the Airport. I would suggest if any future guest do ask, that you simply tell them this is not part of your listing offer as such you are unable to accommodate their request although you are more than happy to suggest a couple of cab services.
If a guest decides to take a holiday or visit a place for whatever reason, it is their responsibility to arrange all transfer transportation. They can seek your assistance as you have a better knowledge of the area and you can givethem details of cabs but you are under no obligations to provide the actual service yourself. Oh well, he is not trilled - but he can't get everything he wants just because he want it.
Don't worry about it, unless they mention it for some reason n arrival, don't mention it yourself. I would say, be alert as this initial behaviour might indicate a demanding guest even one with high expectations so you will need to be firm and establish boundaries from the start if you sense anything like that.
As an additional note, if you do find for some reason that you are getting a few requests for such services, it might be an idea to add a line to your description stating that you do not offer pick-up service from the airport although can recommend a few options if required.
Happy hosting, Ama