Ladies, why would you give somebody your number if you are not willing to answer his calls/texts?

Anonymous
There is this girl I like, she is very pretty and seems interesting, she is not a friend or anything more of an acquaintance. The other night I finally had the chance to talk to her alone, and I asked her out for dinner. She said: "OMG let me think about it, I don't know if I can this Saturday. Maybe next Saturday?". I said sure no problem, please let me know as soon as you know anything (This was on a Thursday night). After that we chatted a little more, she seemed flirtatious after my offer to take her out for dinner. She said she did not know that I was available, so we exchanged phone numbers and said she would let me know the next day.
So, Friday comes and at around 1pm I get a text from her saying: "Hi, thanks for the invitation for dinner, that was very sweet of you. But I can't this Saturday."
I replied about an hour later saying: "That's fine, how about next Saturday?" She never replied.
On Tuesday I gave her a call, she didn't answer, and didn't return my phone call after I left her a message. Then I saw her Thursday night again. She seemed happy to see me, and was talking to me as usual! I didn't say anything about my text or phone call because we were with other people. This Saturday I decided to send her one last text: "I hope you are having a lovely weekend, even though it seems like you have something against returning my texts and phone calls : )". No response either.
Now come on. If you are not interested then why in the world did you give me your number? Why didn't you say oh I have a boyfriend or something along those lines? Why bother flirting with me?
Ladies do you do this often? Why?
Ladies, why would you give somebody your number if you are not willing to answer his calls/texts?
4 Opinion