My kids don't want to talk to there dad, and he blames me.?

i llive in canberra and live 6 hours away from my hometown and the matter is My ex rang me today. I said he is getting wild cause the girls havent contacted him, i have ask the girls several times to ring him, and they have simple said a straight out answer "no, i dont want to talk to him". Ive have asked them why they don't want to talk to him. and they say they just don't want to talk to him. I don't want to force this matter on my girls because i feel i might loose there trust for being a mum. I have rang him and told him that the girls don't want to talk to him and he won't listen to anything i say even if i have tryed to tell him that he needs to come visit them sometimes instead of the girls going to him all the time and maybe he will gain more contact from them and what they have done during school hours. My ex has another partner and has had another child to his missus. Ihave tryed my hardest to get my girls to get along with her as well. Maybe my girls are not ready to see there dad with another person i dont know but all i know he blames me for the girls not contacting him or going to spending time with him when we are home way and now he wants to take me to court for this matter. anyone got any suggestions to how to deal with this matter please its causing me distress and making my depression worser.