Simply follow any one of these steps to prevent your gigaRoam pack from being automatically activated:

1. Turn on airplane mode on your mobile device
2. Turn off 'Data Roaming' in your device settings (usually found in Mobile Networks)
3. Turn off your SIM card in your device settings (usually found in SIM Manager)

For example, you have planned for a trip to Malaysia then Thailand, and have purchased the gigaRoam APAC that you plan to use only in Thailand. To prevent the gigaRoam pack from being automatically activated when you arrive in Malaysia, simply follow any of the above steps.