Random Txt Msg

You won't believe what just happened. Im sitting at home minding my own business and I get this random txt msg. "Hey how r u?" from a number that is not in my phone. I just recently switched phones and have yet to put all the numbers in, so I entered the number in my old phone but got no match. So I write back "who is this?". They write back "Its nikki". So at first I assume that its this nikki from another city that I talk to. But after asking a few questions I soon realize that its not the girl I think it is so I interrogate her further. She tells me "It's anna k's' sister". I still have no clue who this person or her sister is. It ends up she asks me to call her. Im a guy so why not call a female stranger she might be hot right? When she answers the phone I can tell by her voice that shes really young which kind of freaks me out a bit. She tells me her friend was texting random people in her phone and that she currently has her sisters old phone which is where my number was stored. So I ask her how old her sister is. She tells me 15. I tell her theres no way in hell a 15-year old girl could possibly have my number as Im 27 and Im not down for illegal business. Shes tells me that her sister is turning 16 next month and I tell her it doesnt matter its 18 and up. So then I ask her how old she is and she tells me 13. Im like WTF!?!? So in a last desperate attempt to figure out what the fuck is going on I mention the names of 2 brothers I know from around their area that are the only people capable (that I know of) to let my number fall into the hands of eager minors. She replies 'Well I dont know Ill ask her when she gets home from work'. I reply "Ok well Im getting off the phone now".... bad scene