My sister has a language disorder. (DLD). She went to special school. She work in admin for nhs and her manager is saying that she has to answer the phone. She's part of a team and this is only a small part of the role dealing with any enquiries. I think most are by email now. She really struggles on the phone but HR are saying that it is not a reasonable adjustment for her not to answer the phone. I feel this is discrimination against her disability? Can we say this to them?