Rent increase letter from council

Hi there I get this letter every March informing me of the rent increase and it usually always states amount payable is around £11 for the water rates for me to pay and the rent is always covered by housing benefit but this letter says I have to pay the whole lot I went on u credit in June 25 and I wasn’t expected to pay full amount now it says I am I m so worried and anxious I’ve done nothing wrong and nothing has changed at all I thought I had to go on my journal on 6 April to let them know the new rent rates any advice will be most appreciated thank you in advance