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ThunderPhone is prepaid and pay-as-you-go: no subscription and no seat fee. Calls draw from the selected organization’s balance. The agent builder shows the all-in per-minute rate as you change configuration, and Billing History shows the final charge for each call. All amounts below are U.S. cents unless stated otherwise.

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Base agent tiers

Inbound calls, outbound calls, SIP connectivity, web voice widgets, the standard voice library, supported included languages, simulations and testing workflows, monitoring, transcripts, transfers, and keypad actions are platform capabilities rather than separate subscription line items. Usage charges and the optional additions below still apply.

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Optional per-minute additions

Custom voices can have organization-specific pricing. When one does, the custom voice policy and builder’s all-in rate show the applicable amount.

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Prompt size

The first 5,000 estimated prompt tokens are included. Each additional block of 10,000 tokens or part of a block adds: For example, a 5,001-token Storm prompt adds 2¢/min; a 15,001-token Storm prompt adds 4¢/min. The prompt editor displays the estimated size and current surcharge. Web-widget context is capped at 12,000 characters and is appended to the prompt used for that session, so it can move a call into a higher prompt-size block. Call billing metadata breaks out those context tokens.

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Call metering

Normal talk time is measured in quarter-minute increments with a minimum of 0.25 billable minutes. Final call charges combine the immutable tier and options used on that call; changing the agent later does not rewrite history. Language switching is billed from the language actually spoken in each segment, when segment information is available. The configured primary voice-language rate is the fallback.

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Hold time, phone menus, and voicemail

Call segments where the agent is not in live conversation — time on hold, navigating automated phone menus and call screeners, and voicemail — bill at reduced rates, below the agent’s normal per-minute tier. The exact reduced rates are being finalized; Billing History always itemizes the final charge for each call, and the builder’s all-in rate reflects live conversation time.

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Simulations and testing

An AI simulation runs two sides: your selected agent and a simulated caller. The charge is itemized from both sides rather than applying a blanket “2×” multiplier. The launch dialog shows an estimate for up to 10 minutes and requires explicit approval; shorter simulations cost less.
  • The simulated caller uses the Spark rate.
  • Your agent uses its actual tier, voice/language, and prompt additions.
  • A phone-number simulation also includes the applicable telephony leg.
Saved scenario suites and validation runs display their own estimate before or during execution.

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Phone numbers

Provisioning or releasing a demo number starts or stops its monthly billing. Deleting an imported number disconnects it from ThunderPhone but does not cancel it with the provider.

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One-time charges

  • Generated voice sample: 3¢ for a new voice/text/language sample; identical cached samples are free.
  • Other billed operations present an estimate or confirmation before charging the organization balance.

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Balance, top-ups, and spending controls

Add a payment method and at least $3.00 to begin making real calls. Funds do not expire. Manual top-ups add a chosen amount immediately. Optional auto top-up has three controls:
  • Balance threshold that triggers the refill.
  • Refill amount, at least $1.
  • Optional monthly spending limit. When reached, new calls and usage pause until the next month or a higher limit; alerts are sent at 80% and 100%.
The monthly limit remains effective even if auto top-up is later disabled. See Billing and top-ups and the Billing API for account and transaction operations.