How many strikes should I give a girl that gives me her phone number before I delete her contact info?

So I am tired of being flaked on and just getting a number to get one. I usually text a girl at the end of the day or the minute I get her number (in front of her) to make sure the number is her's. I think giving a girl a three strike policy (three text messages) and ONE phone call is enough before you can take her number off your phone--all done on different times. I feel like this way you don't come off as a needy guy.