Units are a simplified way to calculate overages.
The base of a unit was one local call minute.
Toll Free Numbers are $1.00/month more than a Local number. If you have a Whisper plan and you select a fifth number and it is Toll Free, your monthly bill will be increased by $6. If the Toll Free number is within your Included numbers, your bill would be increased by $1.
The base for a Unit is one minute call time through a local number. Inbound and Outbound calls are counted the same. Local Inbound SMS is FREE. Local Outbound SMS, and Local MMS in both directions are one Unit.
Toll Free call minutes, SMS, and MMS, all Inbound and Outbound are counted at 2.5 units.
Call Transcripts are one unit per call minute, for Local and Toll Free alike.