It is easy to lose customers. Just put them on hold listening to tinkly muzak after asking them to press a sequence of buttons on their phones for different options, rather than putting them through to a real person.

Then, when they go online instead, make sure your website is so slow to navigate and difficult to load that they give up in disgust. If you're are really successful, they might just pass the news about your customer service to their friends, too.

As more customers get used to carrying out daily tasks like banking and shopping over the telephone and online, they are also becoming less forgiving of slow service and poorly designed telephone and computer systems.

Increasingly sophisticated technology is fuelling public expectations of what constitutes good service, says Andrew Cooper, the managing director of research company Populus. "People are getting more impatient and more time sensitive."

A survey commissioned by Cable and Wirelss and carried out by Populus last year found that nearly half the men questioned and more than a quarter of the women would wait no longer than three minutes online for a site to load or pages to come up. One-third of women and 40 per cent of men would hang up if they were kept waiting for more than three minutes on the phone. People kept waiting in queues for more than five minutes would give up.

Customers' pet hates in descending order were: automated answering services (press 1 to be kept waiting, Press 2 to be cut off...); telephone muzak; not knowing how long they might have to wait; counter staff carrying on casual conversations while serving customers; and slowness of internet connections.

"What this suggests is that if a company is able to establish leadership in offering quicker service, it will have a competitive advantage," says Mr Cooper.

The reverse is also true, says Annie Garthwaite of management consultancy CM Insight. "Customers are much better at exercising choice than they used to be. If a company is no good, they will change."

CM Insight specialises in advising companies how to set up and run customer contact centres. These are for many people the only point of contact with a company whose goods or services they are buying. Numbers of contact centres are growing by 14 per cent a year in the UK.

Ms Garthwaite says: "Companies' big mistake is to think of contact centres as a cost, a peripheral. But the contact centre is the primary interface of the business. You have people like First Direct who have spent lots of money on technology but make sure it works to support rather than frustrate the customer."

First Direct, part of high street giant HSBC, changed the face of banking in 1989 when it set up its 24-hour telephone banking service in Leeds. With no branch network, it communicates with customers entirely by telephone and, more recently, by internet and text message, all potentially risky as customers get more demanding.

But the bank scores consistently highly in customer satisfaction surveys for its speedy telephone response, friendly staff and efficient service. There is no automated phone service and customers usually speak after little delay to a member of staff who has access to all their different accounts.

Jonathan Etheridge, head of e-futures at First Direct, says: "Of course our approach costs more but it's a matter of how you treat customers. Some companies tend to treat contact with customers as an inconvenience. But we made a decision to focus round the customer rather than what suits the company."

Other businesses have found out the hard way that they need to find out what customers want and deliver or risk losing them to rivals.

Some of Abbey National's two million telephone banking customers started to complain that it took too long to get through. The bank took on more staff, and after talking to customer focus groups, changed its automated telephone answering system. Abbey's Jane Reynolds says: "Some people were happpy with the options on the phone but others wanted to talk to a real person, so we put the option to speak to someone at the top of the list."

Faced with complaints about long queues in branches, Abbey changed staff shift patterns and installed telephones in branches so that people whose accounts were set up for telephone banking could use that service instead of queuing. It has revamped its website after complaints that it was difficult to navigate. "The aim is seamless service whether people bank online, by phone or in a branch," says Ms Reynolds.