It is not permissible to change the intention of ihraam from Qiraan to Ifraad
Question

                On one occasion I intended to do Hajj and ‘Umrah together at the time of ihraam, but when the bus had travelled approximate twenty kilometres from our village I found out that our fellow pilgrims had entered ihraam for Hajj only – i.e., Ifraad – so I did the same as them. Do I have to do anything because of that or not? Please advise me, may Allaah reward you. Please note that I have gone for ‘Umrah in Ramadaan several times since then.
Praise be to Allah.If the change in your intention from ihraam for Hajj and ‘Umrah together to ihraam for Hajj only happened before entering ihraam, then you do not have to do anything. But if that was after you had entered ihraam for Hajj and ‘Umrah, then the ruling of Qiraan was not waived in your case, so your actions of ‘Umrah are included with your actions of Hajj, and you have to offer the hadiy (sacrificial animal) of tamattu’. 
And Allaah is the Source of strength. May Allaah send blessings and peace upon our Prophet Muhammad and his family and companions. End quote. 
Standing Committee for Academic Research and Issuing Fatwas 
Shaykh ‘Abd al-‘Azeez ibn ‘Abd-Allaah ibn Baaz, Shaykh ‘Abd al-Razzaaq ‘Afeefi, Shaykh ‘Abd-Allaah ibn Ghadyaan, Shaykh ‘Abd-Allaah ibn Qa’ood. 
Fataawa al-Lajnah al-Daa’imah li’l-Buhooth al-‘Ilmiyyah wa’l-Ifta (11/162).