Arranging payment and send transfer letter

I would like to find out why it is so difficult to send a transfer letter to another debt review I'm not opposing in paying the amount they said I am owing I even asked to do it in writing if they don't believe that I cannot pay 750 but what is important is that I would be able to pay back my creditors end of the month. I can make an arrangement of paying back their 750 they are charging me with which I'm confused is for what?