Collecting subscribers via a Klaviyo form is a super popular way to grow your subscriber list. (See this article for info on how to set this up.) It is very important to bear in mind that email collection and phone collection have two different sets of rules!
Phone collection requires a double opt-in. In the case of Klaviyo forms, inputting your phone number on the form is step one.
After the subscriber enters their phone number, they'll receive a text within 1-minute.
In order to be subscribed to receive SMS from your shop, the user MUST reply Y! Once they do, they'll receive the automatic compliance language & the reply associated with the keyword you connected to your Klaviyo form (if you created one).
The user is now officially a subscriber and will now show up within the Klaviyo list that you've created as well. You can use those lists to segment campaigns!
Please let us know if you have any further questions or concerns. We're here to help!