Yes, a follow-up call can potentially become a billable GLSA lead if Google treats it as a separate eligible lead interaction. The fact that the original call was not charged does not automatically make every later call free.
Under the October 2026 rules, Google evaluates the call itself, including factors such as call duration, whether it was answered, business hours, and IVR interaction. So a later qualifying call can be charged even if the first call did not meet the billing criteria.