Every device will have their own package.
A package cannot be shared over several devices.
The package cannot be upgraded or downgraded.
A month will be count by 30 days, a year 360 days.
Your current package will be terminated if you want to upgrade or downgrade the package.
Fortunatelly, if you subscribe with the same package, your quota and expiration will be extended and added.
For example :
Your device currently have free package with 900 quota left and expired in 20 days.
You are willing to upgrade to regular package.
Your quota will be 10.000 and expired in 30 days start from today.
The remain quota of 900 and expiration time will be terminated.
Your device currently have regular package with 5000 quota left and expired in 10 days.
You are willing subscribe regular package again.
Your quota will be 15.000 and expired in 30 days start from expiration date, to be exact 40 days (30+10) from today.
The remain quota of 5000 and expiration time will be added.
This rules applies for all packages.