Welcome VA from VA from VA in Rainy Massachusetts!
Sorry that I can't help you with texting; I don't do any text messaging myself. I can help you with your deadbeats

though.
The first thing you need to do is stop doing work for anyone who hasn't paid you for work you've previously done for them. I know this sounds harsh, but if you're serious about running a viable business, you need to show your clients that they can't take advantage of you in this way. Send the deadbeats a polite email message informing them that you won't be able to continue work on project xyz until you've received payment for project abc. If they call screaming, politely but firmly explain that you can't continue on the project until you've been paid for the last project. In the future, demand a down payment from clients who've stiffed you more than once.
Do you have written operating policies that you give to your clients? If so, do you ask your clients to sign a page indicating that they've read the document and agree to it, and do you have them return the signed page to you? If you don't have such a document, you need to create one ASAP. Such a document would include contact information, operating hours, what services you offer, what services you don't offer, turnaround time, upcharges, etc. The credit policies portion of your document should state when you expect to get paid, how you expect to be paid and what happens when you're not paid.
Look at it this way, you call a plumber because your basement is flooded (assuming you don't live in a flood zone). On the phone the plumber tells you it's $75 just to show up and assess the situation, and you agree and tell him to hurry. The plumber shows up and decides your hot water tank has blown its brains out and needs to be replaced. Before doing the work, he hands you a document with a cost estimate that he wants you to sign authorizing the work. You sign and off the plumber goes to get you a new hot water tank. When he's done his work, he asks for payment in the form of a credit card, cash or a check. If you had the audacity to refuse to pay him, he'd drag you into court because you signed a document authorizing him to do the work. Having an operating policies document that includes your payment expectations is no different than the plumber asking you to sign a work authorization.
From my personal point of view, a client that doesn't pay is worse than no clients at all.
=>Donna