The one job of the first message
The first text isn't meant to close the sale or explain your business. Its only job is to get the caller to reply with what they need, so a real conversation can continue by text instead of ending in silence.
What belongs in it
A short acknowledgment that you missed their call, and a direct question: what do they need done? Keep it under two sentences. "Sorry we missed your call — what can we help with?" does more work than a long explanation of your hours or services.
Send it from the same number they called, not a separate system number — replies should land somewhere a real person sees them.
What to leave out
Skip pricing, skip a list of services, skip anything that reads like a sales pitch. A caller who just tried to reach you by phone wants to be heard, not marketed to. The goal is one more reply, not a closed deal in the first text.