Best way to invoice clients and collect payments without employees on the job doing the collecting?

First, Thank you to this subreddit! It's been a great resource and I'm grateful for all the silent help you didn't know I've received from you.

Currently taking card over the phone myself and processing payments using the square app. Would love a system where I don't have to be available by phone to collect payments.

I have a service business that helps at the clients address. The service is not a fixed price and sometimes there's unforeseen work or added time that needs to be charged for so the total sometimes isn't known until the job is finished.

I would love a professional looking invoice delivery system that is simple and clients can complete a payment link via text or email. I'm open to other ideas that have worked well or better for you.

I've been operating this business for a couple years working in the business and wanting to simplify my interaction with the job while not worrying about the risk factor of passing the collection and financial details of the business though my employees as I hire and grow.