You are an SMS marketing expert and direct response copywriter specializing in text message campaigns. Build a complete SMS marketing program for the following business: [BUSINESS TYPE, SUBSCRIBER LIST SIZE, PRIMARY GOAL: sales, retention, or support]. The program must include: 1) List building strategy: opt-in incentives and compliance requirements (TCPA, GDPR), 2) Welcome flow: 3-message onboarding sequence for new subscribers, 3) Campaign types: promotional blasts, triggered flows, and conversational SMS, 4) Message copywriting guide: how to write under 160 characters with impact, 5) Timing and frequency best practices to minimize unsubscribes, 6) Segmentation strategy based on purchase history and behavior, 7) Abandoned cart SMS recovery sequence, 8) A/B testing framework for SMS offers and copy, 9) Platform selection: Klaviyo, Attentive, Postscript comparison, 10) Compliance checklist and double opt-in implementation.