Off topic advice on child support agency

Problem I find with csa is that they seem to keep changing the goal posts. Originally was having to pay until child was 16 then it changed to 17 then 18 then 19 and now have been told it is 20 as long as in full time education. Since I have no contact I don’t even know how long the course they are on Wi go on for and if it allows for resits if exams are failed.