I know how annoying it can be dealing with One-Way Audio issues on some of your Applications. It is pretty strange that it does not work on the Cellular Data but works totally fine via Wi-Fi.
Have you checked out Zoipers forum page related to this topic located Here? We recommend trying some of the suggestions to see if you notice any improvement. We can also attempt some troubleshooting steps on our end as well but we'll need to gain access to your information on file to do this. Please send us a Private Message to @CommunityHelps and we can get started.
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