The SMS habit that costs UK SMBs four figures a month
Most UK SMB messaging started on SMS. Twilio, Vonage, or the original MessageMedia made bulk SMS easy a decade ago, and the workflows around booking confirmations, OTPs, and marketing blasts were built on top of that infrastructure. The cost was acceptable when SMS was the only high-engagement channel.
WhatsApp Business API changed the maths. UK consumers open WhatsApp at 80-95% within an hour and reply at 30-40%; UK SMS opens are 20-30% with reply rates near 3-5%. The same message on WhatsApp gets more attention and now costs less because Meta removed the service-message cap in November 2024.
Where the cost gap comes from
Three places. Per-message base rate: Twilio UK long-code SMS is £0.043 per segment; WhatsApp Marketing is around £0.04, Utility around £0.018. For multi-segment messages (anything over 160 characters) SMS doubles or triples; WhatsApp stays flat. Free service window: every WhatsApp reply inside the 24-hour window started by a customer message is free. Equivalent SMS replies cost full rate every time. No segment penalty: WhatsApp bills per message, SMS per 160-char segment.
Where SMS still wins
Three cases. UK numbers that haven't opted in to WhatsApp (rare in 2026 but real for older demographics). Compliance use cases where SMS is the regulated channel (some financial-services 2FA). Cold outbound to numbers that haven't messaged you first (WhatsApp Marketing templates require explicit opt-in). For most UK SMB use cases none of these apply.
The Twilio-WhatsApp routing pattern
Higher-volume operators run both: WhatsApp as default, SMS as fallback when the number isn't WhatsApp-registered. That pattern keeps the cost gap close to maximum (most messages go via WhatsApp at the lower rate) while preserving deliverability for the long tail. NuvenarHub supports this fallback pattern natively on Pro and Enterprise tiers.