Scottish power debt collector charges

M21

I have debt with Scottish power. It was £300. I couldn't pay so it was sent to a debt collector. I set up a payment plan of £1 a Month but the debt was requested back by Scottish power.
They have done this so many times with a £50 charge each time that it now stands at £650!!!
I'm not sure if I can challenge this as each time I had set up a plan to pay so think it's extremely unfair.
A couple of times they have sent it to 1 collector (incurring £50 charge) and before I can contact and set up DD it's been returned and sent to someone else with another £50 charge!
Please help, does anyone know what I can do or if you have experienced this!!!

[Deleted User]

Your agreement to pay £1 a month is £12 a year and it would therefore take you a quarter century to pay off!

If this is not your only debt, you need to refer to a debt counsellor. Make an appointment at your local Citizen's Advice Bureau.