I have received a letter from mackenzie hall on behalf of Cabot Financial (Europe) Ltd, as I have an old debt that has obviously been taken over by Cabot. They want me to agree to pay £50 per month but I haven't got that much spare each month. They say if I don't they will arrange a DOORSET ASSESSMENT. I am paying £20 per month now as that is all I can afford. This debt is going back to 2005 when I moved abroad and forgot about it. What should I do?