David uses the perfect tense for this verb, which would be literally rendered, I have called upon you.
But because the verse includes the imperatives regarding David’s prayer (Incline your ear to me; hear my words
), it makes most sense to take the perfect tense as an instantaneous perfect, and translate it as the ESV does: I call upon you.
6 I call upon you, for you will answer me, O God; incline your ear to me; hear my words.