Voicemail is the usual answer, and most people hang up rather than leave one. An answering service puts a person on the line, which is better, and it charges by the call. That person does not have your calendar, your prices or your list of jobs you turn down, so what you get is still a message to deal with later.
The common software answer is a missed call followed by an automatic text. It keeps the lead warm, and it leaves the booking, the quote and the follow-up exactly where they were, which is with you.
This finishes the job on the call instead. The question gets answered, the time goes in the calendar, the payment link goes out by text, and the lead is written down and sent to you before you have read anything. The difference shows up as a fuller calendar rather than a longer list of people to ring back.