How can I help my girls?

Hi i have two girls aged 12/13 there father was on benefits he use to try and make an effort now and then.

He now has a full time job and earns quite a lot of money now over the last 5wks my girls havent seen him and had nothing of him i try and contact him al the time but to no joy he has now saying he hasnt got time to see them or he cant never get to the bank to put the girls a bit of pocket in the big 10pound.

He now has his woman who he lives with sending me txts telling me to back of because i ask him to see his girls i would like to have something done about this im not bothered he doesnt see them as the girls arent keen anymore but i think my girls deserve to have some kind of money from him as my 13yr is disabled with autism and it has effiected her routin.