I really want to phone my girlfriend, but iam really really nervous about what to say?

later iam going to phone my girlfriend, but iam a little scared that it might be a bit awkward... i was going to ask her out to the movies, but ive been told not to hit straight into the question so it doesnt look as though thats all iam calling for. But i dont want to phone up and be like "hey its mat, iam i speaking to sarah?" what do i say when she answers? (my phone name wont come up on her phone because iam using my dads because he has free minutes lol)