CSA keep threatening me despite never missing a payment

Me and my ex broke up when my son was 4 years old part of the brake up was over the fact she told me my son was not mine and then cut contact for 4 years!

Contact remade when social services contacted me that my ex has been emotionally harming my son. Discussed with social services that my ex claimed he’s not mine and urged me to get a DNA done. This time of my life I worked very little hours and was broke no help from anyone I saved up for the DNA that my ex refused to have done.

Meanwhile I was paying my ex cash in hand this was also recorded in the social services reports how much I paid and when.

I get a letter from CSA saying I owe 3 months of money to my ex when she made a claim bec in September? Told them I been paying by cash and social services had this recorded. Told me that’s not proof ???? And I had to pay which I did and also explained my ex told me this is not my son and refuse a DNA and they told me that’s my problem to fix.

To this date I am still paying And my ex still refuse the DNA this year alone I have had 3 threatening phone calls from CSA for overdue payments yet I’ve never missed a payment? On all 3 times I argued got put through to a case worker and been confirmed the person that was mistaken yet haven’t stopped them bothering me.

Worst case and point … This year a CSA case worker told me they could of helped with the DNA test when the case was first opened but now it’s to late for them to help. Asked them why this wasn’t explained to me when the case was first opend when I mentioned she refuse a DNA. They told me most likely the person who delt with this case when it first opened Didn’t know that!!!!

Train your F*****g Staff!!