Yes, TeleSign's Telephone Verification API documentation provides suggestions and example code for limiting the number of times a user can request a verification call. Please refer to this documentation, which can be found by logging into your TeleSign account and clicking on the "Integration" tab. TeleSign makes no guarantee that this code will prevent users from abusing your system. Please talk to your programmer about the best way to limit the number of verification calls your users can request. TeleSign has back-end procedures in place to track and prevent abuse, but you are responsible for all requests made from your account.