OmniDex (OMNIDEX LLC, mycontacts247.com) sends account text messages from 1-877-720-OMNI ((877) 720-6664) only to account holders who choose to receive them.
On the Create your account page you enter your own mobile number. Below the account fields is a separate checkbox for text messages to that number. Only you, the account holder, can check it, for your own number. It is unchecked by default and optional: you can leave it unchecked and still create your account and use every OmniDex feature. Consent is not a condition of purchase or service. This is the exact checkbox and wording shown on that page:
Screenshot of the live Create your account page showing the mobile number field and the optional SMS checkbox, unchecked by default (password, recovery email and PIN fields omitted):

No marketing or promotional texts. Msg frequency varies. Msg & data rates may apply. Reply STOP to opt out at any time, or HELP for help.
No mobile information will be shared with third parties or affiliates for marketing or promotional purposes. Text messaging opt-in data and consent will not be shared with any third parties. See our Privacy Policy and Terms of Service.