It could be that you will need to set everything with uci.
I will try to help you out with that.
First of all, send SMS admin01 restore to reset your router fully.
After that, check with admin01 status if router is up and running, if yes - we should start executing these commands through SMS, but make sure you send these commands separately.
admin01 uci set simcard.sim1.auto_apn='0'
admin01 uci set simcard.sim1.force_apn='-1'
admin01 uci set simcard.sim1.apn='internet.public'
admin01 uci commit
Tell me if it works or not.