If a user registered with an email address, they can still bind a phone number after logging in.
After logging into your Bityi account, click the "Account" option under the "Profile Icon" in the upper-right corner of the page.
Select "Security."
Find "Phone Number" and click "Set."
Enter your phone number and click "Send Verification Code." Under "Email Verification," click "Send Verification Code." The system will send verification messages to your phone and email. Please check and enter the codes, then click "Confirm" to complete the process.