In my opinion, you should avoid using the phone apart from when really necessary. The problem with phone conversations is that unlike texting where you can think about your reply, change a word, put in something funny etc.. before sending it, with a phone conversation you have to try and be spontaneous, fun, and relaxed there and then.
Now if your that sort of person naturally, then great but most of us aren?t and it?s very easy to say the wrong thing, or start coming across needy. I?d stick to texts/email to build comfort and attraction and only really use the phone if you need to change date times/venues etc..
Peace,
Rumba!