Where this channel wins
SMS delivers a 80-95% open rate with a typical first-touch window of under 30 minutes. For involuntary churn — where the customer already wants the product — reach is the whole game.
The recovery message has no persuasion job. It has a notification job: tell the customer a charge failed and give them one action.
Cost and constraints
Cost profile is per-segment, varies by country. Carrier filtering blocks links in several markets.
RRLabs is bring-your-own-credentials on every channel, so sending cost is billed to you at provider rates with no markup and no revenue share.
Sequencing it correctly
Use SMS as the escalation step rather than the opener when its cost per contact is high, and as the opener when the decline is time-sensitive — authentication_required being the clearest case.
Never send the same copy across two channels in the same hour. Stagger by at least a day and change the framing.