Hi there,
Apparently there are configuration problems on your phone.
Every time you "change" the provider - that is to say change the SIM, you should receive a "welcome message" or a "setup message" from the provider.
Because you now have various configurations (e.g. from your home country e.g. Vodafone in Germany, Salt and Sunrise from your previous tests) available on your device, it is possible that the device cannot connect correctly to Swisscom.
I therefore always recommend that you insert a different SIM, even if it is within the country to remove the configurations.
Note that the APN settings are adjusted in the "Setup message".
You must therefore reset them and overwrite them with the new ones from Swisscom.
Instructions for removing APN's can be found here: https://my.econnectjapan.com/set-up/uninstall/#android
You can find sample instructions for adding the Swisscom APN on Android here: https://devicesupport.swisscom.ch/huawei/mate-20-pro/getting-started/set-up-your-mobile-phone-for-internet,
Depending on the device, the menu items may vary slightly!
On iPhones it is possible that APNs are automatically adapted depending on the version of the device.
However, you will find a good help here: https://support.apple.com/en-md/HT201699
It is important that you restart your mobile after editing the APN's. Otherwise the device may not be able to dial into the network correctly.
If the APN is configured correctly, you should be able to use 4G at speeds of up to 100 Mbit / s with inOne Mobile Go and with prepaid from around 30 to 50 Mbit / s.
I hope I was of help. Otherwise, please let me know if you need further assistance.
Kind regards,
Dominik