Advice as to when Welfare POA (UK) has disallowed all contact to our mother from friends and family, calls or visits.

My mother is resident in a care home in the UK myself and my brother are in Canada. My sister has been very difficult to deal with in being the Welfare POA in UK, and when we have been trying to support Mum in her wishes to be in a care home in her residence town which my sister has refused to do. My sister has now cut family and friends from phoning my Mum or visiting something I did daily (Call) in a Care Plan citing that we are coercing our Mum to want to go to the care home of her wishes. Is there anything we can do to get contact back with our mother? My sister gives us no updates or medical assessment information and the care home just says Mum is fine. I know my Mum was grateful of my contact and frequently said she was so happy to have my calls and insisted I keep calling.