For websites like Patreon that use Stripe Checkout to process payments, patrons have the ability to use Stripe's ‘Remember Me’ feature. When patrons select this option during the pledge flow and if a phone number is entered, a confirmation code will be sent via SMS to that mobile device.
Then, once the patron inputs that SMS code to pay, their information will be saved with Stripe, and they’ll be able to make payments using this mobile verification flow in the future.
If you received a message from Stripe Checkout but didn’t enter your phone number on Patreon or another website using this feature, it’s likely someone else just entered their own number incorrectly. If this is the case, please just get in touch with Stripe and they'll assist you in removing the phone number from their records.