No letters about being switched from IS to ESA.

I claim IS and DLA due to my mental health problems. Today i have received a letter from the DWP. About your income support. i am writing to tell you that your income support will change.This is because of a change in your circumstances. From 10th may you are not entitled to income support.This is because you have to be available for work.You should claim job seekers instead. Today is 20th letter is dated 16th september,May 10th is 4 months ago and im still getting payed my IS.My cicumstances have not changed either. Im worried sick and dont understand what it means,cannot phone till monday to find out.