pip assessment too far away

I live in Merseyside was offered pip assessment appointment in Preston. I phoned ATOS and told them i cannot travel that far, appointment was made for Liverpool town centre , i told them fine, 3 days later letter arrived that appointment was cancelled given another time and appointment centre in Livrrpool.finally today on my way to assessment in a taxi received text to say appointment cancelled.came home and my son phoned atos they have just offered me another appointment in Preston tomorrow.if i dont go they are sending claim back to dwp what can i do?

You can ring and make a formal complaint.
You have already told them Preston is too far.
Also contact your MP and copy him/her into a formal written complaint.