Father of girl wants me to change my caste to get married

Hi,
I am in love with a girl for about 6 years. We both are of two different castes(both are OC). I dont have parents but i have my family(brother, sisters...). From my side every thing is fine and my family is ok for intercaste marriage. But the problem is her father who wants to give her daughter in the same caste only and i tried to convince him but he is not at all listening to my words. I told that i am ready to change the caste if possible. He is not even accepting to meet him to discuss about this. His main problem is my caste(even i am OC). He just repeat the same sentence that "i don't want to lose my dignity in my family and caste. Now they house arrested her and not even allowing me to talk with her.
Please suggest me an idea how can i solve this.