All of my first customers are scammers :(. Anyone else deal with bad actors using your product?

Feeling a bit bad honestly. I released my first Add-on in the Chrome Webstore (https://chrome.google.com/webstore/detail/sheet-gurus-sms-send-text/caifjmaanhnclfninjjfhbmigekmkeeh?hl=en) and imagine my delight when I got my first 3 customers in the first 48 hours with 0 marketing!

Unfortunately, these ended up being scammers. I reviewed the messages being sent out and the first batch of 50 were sent to incremental phone numbers from some guy pretending to be Verizon and saying people owed money.

I then banned that account and he made another. So I setup a rule on the server that so far has worked in his next few attempts at making accounts.

Then just tonight I see another new user has texted 30 people, mostly deactivated phone numbers, sending some scam bitly link.

So I'm now having to spend more time and money, and embarrassment, sending followup texts to all of the recipients of these people telling them of the mistake.

I also am expecting chargebacks on all 7 of these transactions on Stripe, which will take my grand total revenue for this project to -$105!

Anyone else deal with scammers or people using their SaaS for illicit purposes? Advice? I suppose a good first step for me would be to enable SMS authentication on new accounts; I just hate adding more roadblocks for legitimate customers to get started.