It is good to say no, but don't give the wrong information.Basic nature is seen in the people that if any other person asks them a question, they always try to give answers whether they know or not, when people know the answer to the question then it is okay but if they have a little doubt, then should not give the wrong answer.
Even if a child asks a question to someone but he does not know the answer, still he answers a wrong answer accordingly because he does not want to spoil his image in front of the child, but it is better that you ask for some more time to get the right answer and then answer it after confirmation. In today's digital world you can find the answer to any question in minutes.
Another example of this is, when someone ask for an address or route from us, even here, if you do not know the way, then say no clearly. Do not misguide the person in front of you by showing the wrong path or giving wrong information.