Bought a phone off wish?

Find where the network settings are and try resetting the network. Your phone needs to reset and to redownload a new PRL that's the list of towers that is close to you preferred roaming list. When you activate your phone it should have automatically done that but Samsung's are notoriously for having that problem. Quickly go to your phone carrier and see if they can get it to work properly and if not file a return with whoever you purchased it from and by yourself a Motorola you won't have a problem with them. They don't come with the ridiculous amount of bloatware that Samsung phones come with. And subsequently they have far less problems

Try turning off roaming.

Is it set up with your own account, or is it running on someone elses?

If so, reset it to factory settings and start over.

it's probably a CDMA phone. Not a GSM phone. The US uses CDMA (no sim card needed) and GSM. other countries mostly use the superior GSM (sim cards) protocol. some phones have both protocols. the s10 is probably one of them. you just have to see if you can change the setting to GSM and use a sim card.