That depends on how long before you come back to the US. You have 60 days after your plan expires to renew your plan or refill your account. After that, your account is closed and the sim card is deactivated. Unfortunately, you probably can not select a plan or refill your account online from outside of the US. You already have a plan selected, whatever plan you used last week. You keep that plan until you change it. If you bought a 30 day plan, that plan will not expire until next month. For example, if you started your plan on May 20, it will expire on June 18. You would then then have until Aug 16 to renew before your account is closed. If you come back to the US before then, just renew your plan.
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