Tried to split my company into two to reduce CSA payments

After having £235 taken out of my wages each month my company decided to split into 2 diferenct companies, i told csa this and after 3 months asked why they hadnt started taking money from my new payrol section, i was told i had a new person dealing with my account and he would call me. I was called back very quick and said could i pay the £700 i owed and then money can go out of my wages next month.

3 months later i was call to say money would come out of my next wages and i would be sent paperwork and could i pay anything for the last three months, i said no because i had just had an operation and was due to have treatment for cancer, all he was worried about was getting me to pay at least half the £1200 by credit card.

I’ve asked for time to pay over 2 years, he now wants £350 a month instead of £235 and said i cant pay back over a longer time, an he do this or can i ask for longer time to pay due to finacial problems while im off work during treatment for cancer.