MBD giving me bad credit score

My Cellc account was handed over to MBD after missing several payments. MBD called me to settle my account And promised to clear my record and close my account. I made full payment the called MBD to close my account since it’s affecting my credit score and the lady who was assisting me rudely said to me, “who said we going to close your account “ im so upset and disappointed because i paid every cent they asked for and no one is willing to help me.