People are dumb. Most will read the apology, then write back without reading to the end. To account for this, break your text into three separate texts. Force them to read. Force their brain to acknowledge it. Text 1: Sorry. Text 2: The pickup is in... Text 3: The earliest possible pickup is... Break it down like this and force people to read three texts. I've been a professional writer since the 90s and this is how it works. If you want people to understand, you have to lead their attention every step of the way. Good luck.