Whether you are texting or communicating with women in any sort of way, ALWAYS assume the best. Sometimes weird things can be said that might throw you off or make you think that the girl isn't interested, they might try and trick you like that. Keep your head on your shoulders and keep telling yourself that you know that she is interested and is just trying to mess with you and basically test your game. Stand your ground and make sure you think of smart things to reply with. Make sure you are patient with your replies.
If the girl is genuinely not interested you wouldn't get a number and she would not reply if you did somehow manage to get it. If you aren't replied to, immediately stop talking.