Friendship chat without registration
Seniors have a higher risk of chronic loneliness, but people of all ages can suffer.
It is understood this role will now be performed by Secretary of State Rex Tillerson.
One senior source suggested Mr Trump cancelled because he was unhappy about the arrangements and the scale of the visit.
The abrupt reversal comes despite Mr Trump telling Theresa May in a phone call last month that he would visit Britain in the New Year.
According to Silver Line's website, roughly 3,000 people volunteer to make weekly follow-up calls to those seniors whose loneliness seems especially extreme.
Sometimes people ring the hotline just to discuss the weather or current events. Not all of them discuss their loneliness head-on, but many like to get feelings off their chest in some form or another.