If the plan expires will I still keep my unused GB amount?

Yes. the validity period of the package is 30 days, 90 days, and 180 days.

Take the 90-day validity package as an example: If you purchase a 90-day package, your proxies will become "Paused" status after 90 days, your unused balance will be retained in your account. Once you recharge, the unused proxies will be carried over to the new plan, and the validity period will restart from the day you recharge.