well i have an idea :P
First : for the people on the street just tell them a big NO and tell them also that you will report them to the police they will run away afraid hehehehe

Second : for the people in the airplane try to change the conversation and if they insist just give them a wrong number (remember mobile phone are closed at the airplane they will not phone you to be sure that this is your number) and by giving a wrong number you will have like a small revenge he will ring and maybe an old ugly women will answer and he will have a miserable date