With dificulty - you can go to the Panassonic call centre and they will contact a local authorised tradesman who may or may not call you back - in my case they did not.
When you do get through they demand a £65 payment upfront before saying when they will come. They can only specify a day meaning that you have to spend a whole day waiting for them. I have given up. Also seems they stop traders advertising directly that they can mend panassonics - John Lewis should put some pressure on them to improve. Not a high standard.
George Lees, January 2011