iPhone not unlocking from Virgin Mobile

My IPhone XR was on service with Virgin Mobile. They were recently were purchased by boost mobile. They informed me I needed to upgrade SIM cards. My phone hasn’t worked since and Boost is less than no help. They have supposedly “unlocked “ my phone repeatedly but under Setting, General, About, Carrier Lock it states it is still locked to my carrier. I’m hoping Apple can do something cause I’m desperate. I cannot afford a new IPhone right now. Anybody got any ideas? I’ve reset the phone to factory defaults repeatedly, reset network setting repeatedly.