Arrears Charges?

A previous mortgage company charged me £50 month after month for arrears adminstration even though we had come to an arrangement to reduce the arrears over a period of time. With the current high profile about financial institutions making charges for more than actual costs can anyone advise me as to whether I could make a valid claim to get some of these charges refunded to me? In other words is it reasonable for the mortgage company to charge me month after month when the arrangement is working well and no action is required unless the arrangement breaks down? Many thanks.

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