My Lumia 535 running Windows 10 Mobile has a network problem. I can't lock or force to 3G-only mode. Is there any way to lock 3G-only mode?
To change the highest connection speed your phone uses for mobile data, follow these steps:
- Go to Settings → Network & wireless → Cellular & SIM (or Mobile & SIM)
- Tap on "SIM settings"
- on a dual-SIM phone, tap "SIM 1 settings" or "SIM 2 settings", depending on which SIM card you've set to be used for mobile data
- Change the "Highest connection speed" setting to your liking. One of the options should be "3G only", which I understand is what you're looking for.
For more information about SIM settings in Windows 10 Mobile, see this support article.