This is almost certainly a Peer to Peer use case, despite what The Campaign Registry might claim. 1 to 1 conversations where the user is contacting you is hard

This is almost certainly a Peer to Peer use case, despite what The Campaign Registry might claim. 1 to 1 conversations where the user is contacting you is hard to argue as anything but P2P, you would be best off with a P2P texting enablement provider or toll free texting.