When you call out to someone to get their attention, but they don’t hear you (or pretend not to hear you), it can be disappointing and/or frustrating. Similarly if you send a text/IM/email to someone, it can also be disappointing and/or frustrating if you receive no response.
I love the Lord, because He hears my voice and my prayers. I will call on Him as long as I live, because He has turned His ear to me. ~ Psalm 116:1-2 (NIV)
God never frustrates us, He is always with us, and always listens when we speak to Him. So call out to God and He will hear you, and will answer your prayers.