If a user is enrolled in the Monthly Subscription plan, they may be asked to “add credits to the credit balance”. So, what are credits and what is the credit balance?
Credits are units applied in U.S. dollars to the account balance. Credits are required for purchasing the services and items with Silent Circle. These services include the monthly subscription fee of $9.95 per user for unlimited encrypted voice, video, conference calling, file transfer and messaging between your team's users. Credits are also used for purchasing a Silent World telephone number and when making calls to non-Silent Circle contacts such as landlines and cellular numbers (when available). When consumed, credits are deducted from the Credit Balance.
The credit balance is the pool of credits attached to the Monthly Subscription user account. A credit card is required to apply credits to the account. If the credit balance falls below the monthly subscription cost, the system will suspend the account until credits are added.