PLMN issue on Android

I am in need of a freelancer who can help me with an incorrect settings issue with the PLMN on Android. I am looking for someone who can provide a solution for one carrier only. Ideal Skills and Experience: - Experience in troubleshooting PLMN issues on Android - Knowledge of Android settings and configurations - Understanding of carrier networks and configurations - Ability to provide a clear and concise solution for the issue at hand. - Experince with VOLTE and IMS There is an issue without PLMN in android. Especially in Samsung and Huawei devices with VoLTE. The specific PLMN is not allowed for VoLTE nor DCNR. Issue Description: once the sim card is inserted into the phone, the VoLTE option disappears, while Samsung note 9 and Samsung S22, and Huawei Mate30 pro, Mate10 Pro support VoLTE. The sim card has ISIM application installed, and we tried having only the ISIM, and then we tried with proper config for the ISIM, yet none worked. The network sends back VOPS supported, yet the phone sends Voice domain or reference as CS Only, while the preferred value is 11 (voice over PS primary and cs as secondary) or ps_only. And also, the UE has NF network notification support disabled. And it also doesn’t send class mark 3 and supported codecs. The issue seems to be two things: 1- Out APNs are not added, we added the APNs by overriding /system/etc/[login to view URL] . Yet no luck and the APNs didn’t get created automatically. 2- Volte might have been disabled on purpose for some countries, thus the UE doesn’t consider Voice over oas at all. There is no issue with iOS, in iPhone we can set the APN for IMS, and then the phone can register to IMS. While in android, if we create internet apn as default, supl type, and then create ims apn, then the ims apn as ims type, then the ims apn dissapears. And volte is not available. In order to solve this issue, we will need to troubleshoot all steos in detail and find the solution, weather the issue is the APNs, USIM AND ISIM APP, Network, phone ?