Hello CArnot,
A very Happy Diwali to you too.
The reason we are able to offer attractive pricing plans is because we are able to keep our costs in control. So you pay for only the services you use. Since there's an additional cost (man power costs, punching errors related costs etc) on our side for call and trade the we pass it on to you only if you use that facility in the form of call and trade charges.
This way, we are able to offer a lower pricing to those who are trading online.
An alternative in case you are not at your pc might be to use your mobile to trade. This way you can save the call and trade charges.