Not the father but CSA still taking my money

I’ve had this problem witht he csa since 2003, ive told them that i believe im not the father to the child of my ex partner reason being she cheated on me several times and when we split up we made a private arrangement and then she filed csa claim against me at the time i was claiming jsa and they were taking £5 a week out of my benefit and she was trying to claim that they wasnt as of a result i have had letters from them saying that i owe them over £1,000.

I’ve told them several times that it came out of my benefit and they deny it anyway ive been arguing with them for the past 3 years about them doing a deo which annoyed me as they never informed me they were going to do.

now im trying to get a DNA test out of them but as its them they refuse to pay for it even though the website states they will. now ive got to try and find £500 to pay for a dna test which my ex supposedly according to the csa she “is willing” to do the test. now they refuse to deal with me over the phone cos i have a go at them but they dont know im recording the phone calls.