ESA to UC unable to give informed consent

Please can someone advise me. I am trying to assist someone with a dreaded migration from ESA to UC. It is a lady with mental heal difficulties and her 80 year old mother left to try and sort it out. The person concerned has had a letter saying she must transfer to UC but is currently unwell and in hospital so unable to do this or even considered well enough to give informed consent. We have tried all sorts of options to try and get the migration delayed when she is well enough. But we keep going round in circles before finally someone cutting the calls off. Please help us to get through to the right person.