Sorry for taking so long to reply - I have been on leave over the summer break.
The answer to you question is in essence quite simple -
1. Attention to detail - make sure you keep a good history of customer interactions that are detailed enough to prevent them having to explain who they are and what they bought every time they contact you.
2. Keep your promises - It's such a simple concept that so many people in customer relations don't seem to get - just do what you have told the customer you will do. If you say you're going to call at a certain time, call at that time; if you say you're going to check something and get back to them, make sure you do...
3. Fix problems quickly - Most problems are straightforward. Assess the problem and tell the customer what you are going to do about it, either right there and then, or as soon as is practical.
There is of course a lot more to it than that, but the key concepts are simple. Most customers just want to get what they pay for, and if there's a problem, to have the problem sorted out quickly.
What business are you in Shanila?