All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
If a person appoints someone to perform Hajj on his behalf and sets a condition on him to make Hajj Al-Qiraan (making the intention of consecutively performing 'Umrah and Hajj at the same time in the same season without coming out from the state of Ihraam after concluding his 'Umrah) then he has to comply with this condition. Allaah says (interpretation of meaning): {O you who believe! Fulfil (your) obligations….}[5:1]. The Prophet said: "Muslims must keep to the conditions they have agreed upon." [Abu Daawood] However, if he fails to adhere to the condition and made Hajj At-Tamattu' (making 'Umrah in the Hajj season and then performing Hajj in the same year assuming the state of Ihraam for each one) he has to reimburse the person who sponsored him to perform Hajj on his behalf, the amount of money that he had spent from the time he made 'Umrah until the time he wears Ihraam to make Hajj on the 8th day of Thul-Hijjah. Imaam Ibn Qudaamah said in Al-Mughni: 'If someone is appointed to perform Hajj Al-Qiraan but performed Hajj Al-Ifraad or Hajj At-Tamattu' then the Hajj is correct, however, he has to reimburse the sponsor whatever he spent for the period in which he failed to comply with the condition, like in the case of At-Tamattu' or from the time he failed to wear Ihraam from the Meeqaat in order to perform a given ritual (until the time he wears Ihraam for Hajj)."
Finally, we draw the attention of the questioner that a person should not perform Hajj on behalf of another unless he has performed Hajj for himself. When the Prophet heard a man who said 'Labbayka Allahumma on behalf of Shubruma, which means: 'O Allaah in response to your call I perform Hajj on behalf of Shubruma,' he told him: "And who is Shubruma?" The man replied: 'He is my brother, or he is my relative.' The Prophet asked him: "Did you perform your obligatory Hajj?" The man said: 'No'. So the Prophet told him: "Perform your obligatory Hajj first and then you can perform Hajj on behalf of Shubruma." [Abu Daawood]
Allaah knows best.