Is it possible to bill customers by phone, text or mail if the biz is mainstream?
 

This is for a Mainstream Business. Other than the credit card what avenues are open to merchants to bill customers? I have seen charities accept donations via text message. Can mainstream business accept payments by text too? Does 900 Billing still exist? :helpme

Of course, why wouldn't they be able to?

What companies offer this service?

Most, of not all of the big credit card processors have a virtual terminal for doing just this.