When phone numbers are unsubscribed from a list, either by users replying "STOP" or "UNSUBSCRIBE" to a message, or you unsubscribe them manually through the subscriber's profile page, you cannot re-subscribe them through our import functionality. If you attempt to import a phone number that is already unsubscribed from a list, Tatango will ignore that specific number during the import process.
If the phone number users wants to re-subscribe, they have to opt-in from their own mobile device by text messaging your opt-in keyword to your short code, or they should be added through the "Add Subscriber" API call.
If users unsubscribe from one list on your short code, you will be able to import and subscribe them to another list on your short code. Subscription states are list specific, not short code specific.