All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallallaahu 'alayhi wa sallam, is His slave and Messenger.
The fact that the cost of treatment was not mentioned when you were admitted to the hospital does not waive the hospital’s right to receive payment for the treatment it provided you.
You should ascertain, through the official and lawful means, the amount that is rightfully due to the hospital. There is no doubt that you are not obliged to believe the debt collection company merely on the basis of its claim. At the same time, doubting their truthfulness does not mean that the hospital’s right is waived. Rather, what is required is to ascertain and verify the matter and to contact the hospital.
As long as your father is responsible for your maintenance and you have no wealth of your own, then the expenses of your medical treatment are obligatory upon him. Az-Zarkashi
said in Khabaaya Az-Zawaaya: “If a relative falls ill, the fee of the physician is obligatory upon his relative.” [End of quote]
Similarly, Ash-Shirbeeni
said in Mughni Al-Muhtaaj: “It is obligatory to provide for him - i.e., the relative - the physician’s fee and the cost of medicines.” [End of quote]
Allah Knows best.