Trick Artist is right, u need to flip the script..
For example, if she texts something that could be misinterprated (sarcastisc joke perhaps), take your time with texting back. Let her check her msg to see if she sent something weird.
Usually i never text back within the hour (some exceptions ofc) mid-day. After 8 pm, i try to up the tempo, so she goes to sleep dreaming of me. (in weekends, try avoiding texting, because if she's out, then she won't text back any time soon. Usually.. And since YOU want to be the one that is controlling the tempo..

)
You can neg her about some joke she makes as well. If she tries to explain her joke for example, take your time. Make her wait and get nervous for loosing you, because she texted a stupid joke (ofcourse we aren't that stuck up, to ditch someone for 1 bad joke, but don't let her know that

).
Try avoiding texting twice in a row within 48 hours. It may come off as needy, which is the last thing you want to display yourself ofc..
Conker, if she doesn't reply to a missed phone-call, and he calls again, he might loose value in her mind. That's why texting is such a powerful tool in the beginning of any relationship. If played right, she will ALWAYS pick up her phone when you call. (But don't call during 9am-6pm

)
CAMo, what I would do:
Send a text somewhere before 7 pm, the earlier the better maybe in your case. Get a text conversation flowing, do not reply within an hour, maybe 2.
After 7pm, try to build up the tempo slightly. Build the conversation to a high-point. Then call.
I don't know the girl. You can just ask her to grab a drink to "enter inside joke between you 2" on a high-point in the phone-call,
or the indirect way of asking out like:
"im going to buy some sneakers saturday, and since i need a female opinion anyway, u should come. Unless u have bad taste..do u have bad taste?" - "response" - "OK, u know (coffeeshop)? Meet me there at 3pm."
It depends on her character which way u should go...
Oh, and don't hang up right after she agrees to go out. Chat for another 5minutes, then hang up. Don't let the 'asking-out' be framed as a big deal, or high-point of the phone-call. It's more a logical thing, because you 2 get along so well.
For text-game, check the topic "How to ask her out by text message?"
Maybe some usefull stuff there