Always agree when possible. Trying to correct or inform your loved one creates agitation.
Tell your loved one the person is either resting, gone to the store, will be back in a little while, etc.
Meet your loved one in their reality. If they wake up and think they are 30 years old again and getting ready for dinner in their home town with their family, meet them right there and go along with it.
Distract your loved one when they ask to speak to someone who’s no longer alive—for example, go outside and water the plants, turn on the TV, or go get an ice cream cone.
If your loved one is adamant about speaking to this person, get them on the phone with someone who can pretend to be their mom, brother, husband, etc.