why company lose customer, it is just personal opinions:
 
Familiar with their products is not enough

Overstate the benefits of products and services

Ignore the rights of the client, hide product matters needing attention

Bad faith

There is no fixed way to trade

After clinching a deal not to follow up, after-sale concept is poor

Don't respond to customer information or phone

Ignore the customer's problem

Once refused, give up and not insist on

Listed above, which you've taken?