Hi Jacob
I'm afraid the DWP can insist, in certain circumstances, that a claimant must have an appointee, even if the claimant does not want one. You can, of course, argue with them (and you should do so if this is not what you want), but be warned, they are likely to say they are working in your best interests. You should repeat what you have said here and ask them to make reasonable adjustments and see what their response is.
BIS
Nothing on this board constitutes legal advice - always consult a professional about specific problems