Hi and Welcome to the forum, you might want to have a look at the following FAQ which explains where everything is
Welcome to Benefits and Work You are still allowed to change the appointment once without penalty - as long as the Assessment Provider admits that this was their fault.
You might like to take note of the advice in this link
benefitsandwork.co.uk/forum?view=topic&catid=10&id=107189 If you have further questions during your PIP process, please reply to this message and we will do our best to help