in England, how to prove you didn't spend Cost of Living Payment

I need legal aid and should be eligible but am slightly over the limit. I received over £1000 in cost of living payments a few years ago. they are discounted indefinitely. legal aid want me to prove I have not spent them because then I would be under the threshold. I have told them I don't know how it is possible to do that because they went into my account which has other money in it. I have over this £1000 now and had over £1000 at the time. what do I do?

they won't accept 'I don't know how to prove if I spent it' and they want me to say if I spent it or not. But money is like water there is no way to tell. what do I do? I need this legal aid