In order to change your plan duration from 1 Month to 3 Months or from 3 Months to 1 Year within the same package.
All you have to do is simply:
 

1. Cancel your current subscription and once the duration of your current subscription is completed.
2. Re-subscribe to MBC Shahid choosing your new preferred plan.

To know more about how to cancel your subscription. please view the following article:

How to cancel my subscription?