Denial of Service with Samsun Ultra Phones

Keep getting denial of service by T-Mobile on SamSung S22 and S24 Ultras'? Message appears stating "Your phone's not registered on a network, so you can only make emergency calls."  Same message both phones.  T-Mobile customer care is clueless over 25 calls in 6 months and no lasting solutions! Purchased and installed a 4GLTE Cell Spot Booster piggy backed on my FiberOptics provider? still same message.  Totally unreliable service. Never know its off the network until I attempt to make a call.