Been fine with Smarty for months then at some point in the last week I've been unable to make or receive calls. Had this before with a porting issue last year which Smarty kindly fixed.
This is likely due to Smarty's parent network Three switching off 3G in your area. The S10 is not on Smarty's list of incompatible devices (see here) so can you see an option for switching on VoLTE (4G calling) anywhere in your phone settings?
I have a SG J4+ and the Mobile network status also states 'Disconnected' (and I am able to use a VoLTE network) . As long as the 'Mobile Voice Network Type' and 'Mobile Data Network Type' states 'LTE' then you should be able to connect to the '4G' network.
As your daughters phone works, and is also a SG, then it may be worth being side by side and going through each of the 'Settings' options together and comparing if there are any difference between her phone, that works, and yours to see if there are any differences that may be stopping the connection ๐ค Good luck x
