Many services allow you to send real SMS or make calls over Wi-Fi without ever asking for payment information.
Offers a real phone number for free texting and calling from mobile apps or a web browser.
If you are looking to create the or a visual mockup: TextMe - Unlimited free texting and calling to any phone no credit card
A popular choice that provides a free U.S. or Canadian phone number for unlimited texting and calling over Wi-Fi.
While it's unclear if you're looking for a way to send messages without a credit card or a tool to generate "fake" text image, there are several ways to do both. Many services allow you to send real SMS
If you need texting for a business, several platforms offer free trials with no credit card commitment:
Allows unlimited texting to the U.S. and Canada and provides multiple phone numbers within one account. Business Texting Trials or Canadian phone number for unlimited texting and
Allows you to test business messaging with free credit and no credit card needed. Text Content Generators