@blkgixaHave a look at this thread if you are using an esim as it should help:
If it does not search yescrowd for "iPhone 12" and see if other people have had the same issue(s) and how it was resolved if it was able to be resolved.
Hi @blkgixa, sorry to hear about your ongoing mobile connection issue. Have you tried changing to a 5G sim card instead? Most of our customers have come back advising that this has fixed the issue. You are best to drop to the closest → Optus store and ask for a replacement 5G sim card. There is no charge for it.