To be called upwards by God is God calling us out of darkness into his marvellous light. In 1 Peter 2:9, the Bible says, we are a chosen generation, a royal priesthood, a holy nation, a perculiar people, to show forth the praises of him who has called us out of darkness into his marvellous light. God has called unto a higher task of being obedience to him at all times and fellowshipping with him.
God's call becomes dim in our hearing when we disobey him, when we don't spend enough time with him and also when we allow the things of the world to take the first place instead of God.
We can renew our hearing of his call by spending quality time in fellowship with Him i.e. in worshipping Him, in Bible studies, Prayer and Fasting and listening to the still small voice.
The contents of this call is to be obedience to Him and serve Him with our whole being.