When you upgrade your Twilio account, unused minutes are credited at a rate of $0.03 per minute, allowing users to convert them into cash-value for purchasing Twilio services, rather than losing them. This change applies to accounts that have been upgraded from the trial period, which initially offers 1000 free minutes with a pre-roll and PIN code requirement for inbound callers. To manage multiple applications or exceed the initial 1000-minute limit, users can sign up for separate Twilio accounts, allowing them to keep track of debugger, minutes, and billing separately.