Need a recommendation: A new Texting App for iPhone 11 Pro

I work in sales. My customers text me orders throughout the entire day. Why has Apple not addressed the ongoing issue of giving users the ability to read a text and then mark it unread, or flag it as a reminder to address the text. For my job, the ability to mark a text to address later is critical. Years ago you could do this and why the feature is not available makes no sense to me.

For that reason, which text app should I look into as a replacement? I don't mind paying for an app as long as it seamlessly integrates well with IOS 14.0.1