my suggestion for you, turn off VoLTE inside phone setting, then you should very fast & easy switching 4G & 2G
anyway, in future Celcom=Digi since they already merged
Before this it’ll drop down to 3G and back to 4G after call. No issues.
Nowadays it’ll go to 2G and then stay stuck there.
My grandmother is using Nokia 6300, she very noob is all of this, but she receives a lot of WhatsApp calls from uk and aus and it doesn’t come through when the DiGi is stuck on 2G
She dunno how to reset the phone, and DiGi doesn’t support volte for her phone.
Celcom is the only network so far I see that actually has volte support for this feature phone so hopefully it’ll alleviate the problem for her.