This is the essence of tawheed (monotheism), that only Allah can hear your dua and only Allah has the power to grant it.
‘Is He [not best] who responds to the desperate one when he calls upon Him and removes evil and makes you inheritors of the earth? Is there a deity with Allah? Little do you remember.’ [27:62]
Prophet Muhammad (peace be upon him) said, 'dua is worship.’ [Abu Dawud: 17:1465]
In Islam, we know that worship directed towards anyone other than Allah constitutes as shirk [i.e. making partners with Allah] and is the biggest sin which a person can commit. View full size (1440x1200) http://dlvr.it/9qp6kb