Can I suspend the monthly charge to reactivate it at a later time?

You can cancel your lines or switch to Lifetime plan.
If you decide to cancel your lines, then later you can reactivate them.
If you decide to switch to the Lifetime plan, you will not need to pay monthly charges. However, it's one way switch and not able to get back to GoFi plan later.
Mind, if you decide to cancel your lines or switch, you will lose the remaining data on your balance.