Credit Score Nightmare

In the year 2016 when employed I opened an account with TGF and I was paying it well then fast forward to April 2017 I got laid off, I then communicated with TFG customer services people and told them as I am currently unemployed CAN we come to an arrangement of how much I can pay as I was unemployed. We agreed that I was to pay 150 and I did. Imagine my surprise now when I get a letter stating that my profile has been handed over to the credit bureau. SO BASICALLY I AM BLACKLISTED after I had communicated with them about the situation I was in.