SMS invites are sent by our users, so the sender has your number in their phone contacts. To maintain privacy we anonymize all contact data and therefore can not share with the phone number of the person who invited you.
After you join, the app will connect you as a “friend on Open” so you can chat with them. You can start a conversation and they will see it, and you'll see them. All interactions on Open are anonymous so you may never know exactly who it is you are talking to.
If this did not happen, let our support team (firstname.lastname@example.org) know and send them your name and the phone number you have used to sign up and we can investigate.