via e-mail or USPS (letter)
<Subscriber Name>,
To enhance the security on your <provider name> account, a temporary PIN has been generated. Please call our customer support department at <customer support number> to confirm your PIN. This process helps us to protect your personal information. We sincerely appreciate your assistance.
Regards,
<Provider Name> Customer Support
via SMS
<Provider name> has issued PIN <#> for your account. Please call our customer support department at <customer support number> to confirm your PIN.