Bad client service

I went to settle my account and the lady who was helping me settled a wrong account on 07/04/2018 and she said she will sort it out on Monday last week. To date I’m still struggling to have this matter resolved and they dying that it’s not going to make a difference which account I pay of first since the balance is the same my concern is they didn’t do what I want the account I want to settle is 30 months while the other one is 24 months which will be paid off in July this. I’m very unhappy about their service and they are not even remorseful of their wrong doing.