First off, I have never seen a patient as my "customer" even though that is becoming hospital newspeak. People who are sick and need to be hospitalized are patients. Second, I think you have to do what you can. Take care of your priorities first. Don't delay a medication for one patient, say, if another is demaning that you bring her fresh coffee. It can be difficult, but you have to be polite, courteous and firm. Saying something like, "I will check back with you in an hour," and then leave the room.
Patients are difficult and demanding for any number of reasons. For some, it's just their normal personality! For others, they are frightened, confused, in pain, depressed and so on. But healthcare being what it is, you can't be a person's private maid service. Spend as much time as you can, trying to find out where the problem may lie. But then you have to move on--and as I said, you never delay essential work with another patient.
Hope this helps.