How to stop husband's visitation rights under muslim law

My husband and inlaws mistreated me so i took khula from sharia court in 2016 when my son was 6months old. I wanted him to leave his rights over my son at that time but he dint. He and his 2 relatives can come to visit my son at a time at my home. My son always cries and never goes to him neither he shows love towards my son during these visits. At the 4th visit he got 1xtra person so total of 4 persons came to visit my son for which we said he his mother and sister, only 3 can come at a time. They all started fighting at our door and accused that the child is not his. After insulting and fighting with us they left threatening us. We got NC done at police station under sectn 504. My question is how can I stop his visitations and get sole custody.