I have contacted two cousins in the United States and Northern Ireland by telephone.We'd never been in contact before but when I called I said that "This concerns genealogy..this isn't a crank call or some scam.
It worked both times and we had long lovely conversations and continue to email and are friends on Facebook.
The word genealogy or family history seems to break through any concern.
Hope it helps.
I have also called on behalf of other people searching in Canada for their family.They lived in England and I thought I could help as I live in Canada.Solved some brickwalls that way!