Much more likely it is a close female friend; someone calling to tell you that they have split up with their boyfriend again or locked themselves out of their flat, or perhaps simply that Carry On Camping has just started on BBC1.
Such friendships are about intimacy and trust and are being increasingly relied upon to sustain people in an age when families are spread far and wide, and marriages fragment so easily.
Erika Reed, a 32-year-old solicitor, is nurtured by her 10-year friendship with her married friend Jane Mee.
"I was very ill one night and so I rang Jane at about 3am," she recalls. "I wanted to ask her what she thought was wrong and told her all my symptoms. She was very supportive and even came round to take me to the doctors the next morning. When you live on your own, the fact that she came round to make sure I went was great."
Since the huge popularity of the American sitcoms Seinfeld and Friends, with their idealised picture of upfront camaraderie and knowing banter between pals, the status of platonic friendships has reached an all-time high. You may fall in and out of romantic relationships, these shows imply, but you had better keep those old buddies on side if you want to survive.
Tonight strong female bonds enjoyed by people like Erika and Jane will be celebrated on the small screen in the first installment of a three- part BBC drama called Real Women. Written by Susan Oudot and taken from her best-selling novel, it charts the lives of five former school friends and puts their relationships with each other right in the foreground. For once, family, husbands and work are all purely incidental.
The actress Francis Barber who plays Anna and stars alongside Pauline Quirke, Gwenyth Strong, Michelle Collins and Lesley Manville, found the script reflected her own experience. "Friendship is about commitment and loyalty," says Barber. "I don't think it matters how far apart you are. I don't see some of my friends for ages, but when we get together it is as if time hasn't passed."
The characters are all modelled on elements of real people in the writer's circle. One is in an unfulfilling marriage, one is a career woman, another is a "good time girl", one is hoping to have a child, and the fifth, played by Manville, is a closet lesbian. "Real Women is inspired by lots of people I know," says Oudot. "One friend said to me, `Every story that we've ever told each other is in the book,' which is true."
With Erika's family 200 miles away from her London flat, it is Jane who keeps a spare set of keys and waters her plants and feeds her cat whenever she is away. "Having Jane around gives me a certain amount of freedom. It is not the kind of thing that you could ask anyone to do, but she knows I will do the same for her."
What is more, Erika says she would not even have her flat in the first place were it not for her friendship with Jane. "When I was looking for somewhere to buy, she was the person that I would turn to for approval. Buying a flat is a very big thing and if your family were close by they would come and have a look with you." Erika feels that because she no longer sees her family in an everyday way she now enjoys that sort of relationship with her best friends. "I can be stroppy with Jane because I think we are close enough. I will actually say if I'm a bit annoyed, whereas when I see my family these days there is never a cross word."
A supportive circle of women inevitably expands to include friends of friends too. Jane and Erika have helped each other's chums to find both jobs and practical solutions to smaller scale dilemmas such as the name of a good plumber.
Jane and her husband may move away from London soon, but the prospect of leaving such a support system of friends worries her. "My friends have more to do with my life than my family and therefore I don't have to go through endless explanations," she says. "Friends are more up to date with what is happening."
Like Erika, however, she is still emotionally close to her family and has a long-term licence to behave a little temperamentally with them. "You are more careless with your relationship with your family," she admits. "While I suppose you have to nurture your friends a bit more."
The modern emphasis on personal happiness rather than on family duty looks likely to continue to steer people away from daily involvement with their relatives, yet for Rebecca Cavanagh, a 32-year-old book editor, it is crucial that a friend should offer more than bland reassurance. "You don't need a friend who is as judgemental as a family member might be, but you don't want someone who is accepting of everything.."
Rebecca, like Lesley Manville's character in Real Women, has recently decided to tell close friends about a new gay relationship. Telling friends first, she says, made it easier to talk about it with her family. "When I first got together with Annie I knew I could tell my close friends straight away, while with my family - even my sisters - I was not quite so sure."
With all the benefits of sisterhood, of course, come the headaches. Women, unlike men, must never forget their close friends' birthdays. And then there is the fraught question of who to nominate for your BT best friend telephone discount.
`Real Women', BBC1 9.30pm