Does any Swiss network be ok with this watch? Someone wrote that Sunrise does not support this

Hello, I am currently trying to set up the watch. I can use it to make calls and write and I can load contacts onto it. The school modes don't work, I can't find a location and I can't find the watch with Bluetooth either. The app reports that there is no connection to the watch. We have a prepaid SIM with swisscom network. Can anyone tell me what the problem is? Thank you

Can you use a Nano-Sim from any supplier? And does it need data and phone network reception?

what kind of mobile subscription is needed to receive or send voice messages? and what kind of subscription is needed to make phone calls?