Simply you aren't building enough comfort...
You need to understand a few things. Having a girl's number is not your goal. Taking her number should be just a way to time bridge that is to arrange a date. Second thing is that n-closing is not difficult, and many HB's will give their number but never reply. There are some nice routines for n-close in just 30sec. But 95% of the time she will flake... So, the point is that you need to build some comfort with her before n-closing. You should even get to the point where you set up a date while talking to her, and than n-close just in case that something goes wrong. That should be in your mind always - her number is not my goal, sleeping with her is. And when you understand that just act according to that line...
To summarise, you got their number too early, and haven't built enough comfort needed for her to go out with you. IOIs should not confuse you. It's a good sign which you should use in your advantage and start creating comfort with her, arranging a meeting and then n-closing. Building comfort through text messages and phone calls is difficult. Do it in person. That should do it...
