Why can't you win a customer of your competitor although you offered him a better price, quality and service?

While price, service and quality are essential factors, they do not necessarily lead to sales due other factors like:

 

Customer loyalty

The customer might have been purchasing for the competitor brand for a considerable period of time. He might also be pleased with the quality and service provided, so while you are offering him a better deal he might consider it  risk in his mind. He is gambling with a certain product and your assurance alone cannot break through the security barrier created in his head.

 

Brand name, reputation and goodwill

A great brand as an example for this is Apple. They have, over the years created a persona for themselves, they are an aspiration creating brand. Majority of the people want to own it and the ones who do feel that their service is unmatched. Now, even if there is a new brand in the market or an existing competitor of Apple's with an improved product (Better maybe), the "Apple Fanatics" wouldn't convert their loyalties without putting up a tough fight

 

The key differentiator

While Coke and Pepsi might have everything in common, their fan base clearly separates them. The one ingredient that makes Coke less sweet plays an important role for them. The one's with the sweeter tooth flock towards Pepsi while the others prefer Coke(Assuming: everyone chooses one of the two). So while your product might be virtually the same, in fact better in many aspects, it doesn't top the competitor's in terms of what gives maximum utility to the customers

Most likely his loyalty to your competitor. However if the price differential is substantial, he can be won over.

Loyalty and fear of change can be prime reasons, in this case a free demo and good after sale service play a vital role in customer attraction

you should know about market and servies

 

Because of lack of trust, reputation and PR

There is one point left beyond Shipra's excellent answer, and it has to do with the cost of switching, which can be illustrated with a very simple example that goes far beyond loyalty.

Are Canon and Nikon 'fans' that loyal to their favorite camera brand? To a certain extent, yes. But far beyond their loyalty, the switching costs are immense, since there is no portability across these brands. What if you feel that the other brand delivered a great camera body? Hold on, before switching, how much should you spend on new lenses, new accessories, new .. new .. new .. and expensive gear?

The same applies to many products, and to services as well. Buying a new product from a different vendor might just be the initial visible cost, and might be a fraction of the cost you would face to migrate to this new product (or service).

To the extreme, the switching cost might be this high that it would prevent any reasonable alternative to the incumbent. You might lower your price to zero, and still be unable to beat the incumbent.

 

This must be appreciated before hand, to evaluate if you stand a chance to win a new client, with the quality of your product/service and the competitiveness of your price.

 

We have to give them more satisfaction then the competitor do.More than that politeness is the only way to get it done.

Passion of the customer to the other business cause to this scenario. To win a customer from our competitors as a business we must always keep in touch on customers needs and wants and competitors strategies they used to attract customers. And continuously we should update our marketing plans.  

It depends on what kind of marketing you provide. Our buying habbit derives from our buying experience. Not just base on the product or services that you offer but also the kind of interaction they would experience. They may already develop a feeling of being at home. And this is of having great sales staff or customer service or employees which is at the frontline. So it is always important to make employees attend some seminars or training to enhance their skills on interpersonal customer interaction.

You need to understand the actual need of the customer by probing . Must be your competitor  is giving him credit facilities which you have not offered. 

The price & service quality are only 90% of the mission...There is also the customer loyality, previous experiences & the manner of approaches made to the customer that will make him support your approach & encourage him to support you & this represents the remaining 10% of the mission.