You can send bulk SMS from the SMS page in the dashboard using any UK caller ID on your account. If you send these from a UK landline number, you won't be able to receive responses.
You can send SMS from the Yay.com apps from any UK mobile number you've purchased from Yay.
If you need any further help today, please don't hesitate to contact our friendly support team on 0330 122 6000 or by email!