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Documentation Index

Fetch the complete documentation index at: https://docs.nixflex.com/llms.txt

Use this file to discover all available pages before exploring further.

Nixflex charges per minute of voice and per SMS message. No setup fees, no minimums, no surprise charges.

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Voice

PlanPer minuteMonthlyBest for
Pay-as-you-go$0.08$0Testing, small apps
Starter$0.06$99Production apps up to ~30k min/month
Scale$0.05$299Growing apps, 30k–100k min/month
EnterpriseCustomCustom100k+ min/month, dedicated support
Voice is billed per second, rounded to the nearest second. A 1m23s call costs 83 × ($0.08 / 60) = $0.111.

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What’s included in every minute

  • Speech-to-text (AssemblyAI / Deepgram)
  • LLM reasoning (Claude Haiku 4.5)
  • Text-to-speech (Inworld TTS Max)
  • Real-time engine processing
  • Call recording (stored 30 days, signed URL access)
  • Post-call analysis (summary, sentiment, custom extraction)
  • Webhooks
  • Dashboard access
There are no separate per-feature charges. Everything is in the per-minute price.

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What’s not included

You pay these directly to the underlying providers:
CostWhere it’s billed
Phone numbers (Twilio)Your Twilio account, ~$1/month per number
Voice minutes (Twilio)Your Twilio account, ~$0.013/min for UK→UK
SMS messages (Twilio)Your Twilio account, varies by destination
Because you BYO Twilio, Nixflex doesn’t see or mark up these costs. You get Twilio’s wholesale rates.

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SMS

Nixflex doesn’t charge for SMS. You pay Twilio directly at their standard rates:
RegionPer message
UK domestic~£0.04
US (after A2P 10DLC)~$0.0075 per segment
InternationalVaries by destination

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Comparing to alternatives

ProviderVoice per minute
Retell AI$0.15
Vapi$0.13
Nixflex Pay-as-you-go$0.08
Nixflex Scale$0.05
Same quality (Deepgram, Claude, etc.) at roughly half the price. The savings come from running our own real-time engine rather than reselling someone else’s.

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How billing works

1

Top up credit

Add credit to your account from the dashboard. Minimum top-up $20.
2

Calls and SMS deduct from credit

Each call deducts at the end. SMS deducts when sent.
3

Low balance alerts

Email when credit drops below your threshold (default $20).
4

Auto-top-up (optional)

Set a payment method to auto-top-up when balance falls below a threshold. Never run out mid-call.

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Usage tracking

Check current usage: 
curl https://api.nixflex.com/v1/usage \
  -H "Authorization: Bearer KEY_ID:KEY_SECRET"
Returns total minutes, calls, SMS, and credit balance.

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Volume discounts

Above 100k minutes per month, custom pricing applies. Contact sales@nixflex.com for a quote.

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Refunds

If a call fails due to a Nixflex error (not Twilio, not your endpoint), we credit it back automatically. You’ll see refunded entries in your usage logs. For larger billing questions, email support@nixflex.com.