received wrong information request

hi i am transferring from dla to pip and have competed the how your disability affects you form and returned it along with support letters etc from gp and consultants etc also included a request from gp for home assessment due to severe mental health problems but within 10 days i have received a letter to go to an appointment at assessment center early next week on 3 separate trains so i phoned them to request the home visit but was told my case file was locked and if i wanted a home visit i needed another letter from gp to confirm this, i also had another letter to confirm they had requested further evidence from the contacts i provided. then today i have received a letter from capita and enclosed is a request for evidence form to be completed by my gp and addressed to me calling me doctor , i have taken this to my gp and he is not happy that they sent it to me at all and advised me to contact them to complain and request a new form be sent out to my gp as he can not complete this one addressed to me . can i now request the appointment for monday be cancelled as they would need to resend the evidence request to my gp and it would not be available in time for my assessment for them to make a fair decision on my claim without all the evidence they need .many thanks.

thanks gordon, the original letter was a statement that it would cause me a great deal of stress to have to travel to a assessment center and a home visit would be more beneficial, i have been back to gp for another letter to request the home visit as capita requested on the phone but it is another £15 i must pay so not happy, anyway i will forward this as soon as i get it from secretary then see what happens.regarding the appointment on Monday can i phone them on friday to move the appointment and state the fact they sent me the report that should have gone to the gp and due to this the report would not be available for the hcp to read at my assessment. i phoned them to explain about the gp report and also sent an email to capita so i have proof. should i email them and request they cancel my appointment until they have been back in touch with my gp and have received the doctors further evidence form back after all it was their mistake in sending it to me in the first place,

thanks gordon, will the people on the phone be able to grant me a taxi if my home visit is refused. bb