Nurses – at least initially.
If your loved one is in hospital, there will be many staff looking after them, including:
But the nurses are there all the time, and often have the best overall perspective of what is going on (especially the plans for discharge). So, if you ring a ward, and need information, it is good to start with them.
If you need to speak to anyone else, they can either go and get them (if they are on the ward), or ask them to ring you back.
For this reason, make sure (via the ward clerk) that the hospital’s computer has your number on, as well as the patient.