My samsung ace 2 x keeps on saying unregistered sim and Ive gone to Mobile networks and selected GSM/WCDMA (auto mode) and I've taken the sim card out and put it in again as well as the battery. I've also Gotten a new simcard but that hasn't worked either..
If you've replaced your SIM and it's still not working, then I think the SIM reader is malfunctioning. Here's your options:
1. If it's under 15 days, you can return/exchange it. If you're past that but under 30 days, then you can make a DOA exchange for the same model only. If it's past that but under 1 year old, you can get it sent out for repair at a Koodo shop.
2. Look into upgrading your device. Check your Tab balance. If it's reasonable enough for you, you can pay that off either in Self Serve or by having it invoiced to you at the kiosk and you can get a new phone for "free". :)