Accessability at F2F center

Hi everyone, my apologies if this has already been covered, I have had a look and couldn't find a answer. In September, my local ATOS office phoned with a apt for a few days later, a new office in my home town. I asked if it was a ground floor office, reply was no. Ah, ok I said, I have great difficulty using stairs...Oh,..was her reply, I then asked if there was a lift, there was. Fine then, Oh no said the lady, I cant let you come here as it's a health and safety issue now,
I was told I needed to get a GP's letter to confirm my mobility issues in order to have a home visit, which I have done and they have received. New apt arrives today, for the same centre! However they have agreed to send a taxi for both journeys??!! So what do I do now? If the lift isn't working, I would be in no fit state to go through with the interview having gone up the stairs on my rear end. Or god forbid a fire broke out, I would be in danger myself and to others.
What do I do?
Thank you for reading