Wi-Fi Incoming Calls

Hello , Help please I have been a Smarty customer since May25. I have an Apple iPhone 14. Sim only . Phone  software up to date .

Wi Fi calling ,incoming calls, go to missed call and a text is sent . The phone does not ring . I have done all the standard checks with Smarty , Wi Fi . Router. No change . I now use phone with Wi Fi calling switched off. Phone works fine with Cellular and Internet working fine . Smarty Technical have the issue now . Just ask same questions again . Anyone any ideas please ?