To change the email-to-sms address you need to do the following:
Go to your Profile Settings.
Click the Edit button and enter the email-to-sms address in the Email field.
A 6-digit confirmation code will then be sent to the specified email address, which you’ll need to enter in the Verification code field.
After you’ve successfully confirmed the email-to-sms address, you’ll be able to receive messages about triggered alerts to this address.
If you use auto-trading services or for whatever reason you can't get a verification code to the specified address, try using webhooks to receive alerts.