How to "split" two 3g modems?

Question

WiFi

Hello. Two 3g modems for two different users living in the same multi-storey building, one lives on the first floor, the other on the second. Both use modems through WI-FI routers. If both routers are turned on, then on one of them the signal is so weak that you cannot access the Internet. It is impossible to predict which of the routers and modems will not go online, it seems it depends on who connected first and who has stronger nerves. When you disconnect-connect, reboot, the situation repeats. How to fix this problem, is it possible to somehow make both users fully use the services of the provider. Thank you.

Answer 1

Change the channel or WiFi frequency in the settings of one of the routers.