Samsung Android not recognizing home WiFi network in Airplane/flight mode only. Why?

I am living in my secondary home, using my Samsung Galaxy Note 8and a DSL router transmitting at 2.4 Ghz. I have free data roaming, free texts but paid voice calls. To minimize my bills, I put the phone (Android 7.1.1) in airplane/flight mode, turned on WiFi and that’s when the problem began. In Airplane/flight WiFi mode, the phone does not recognize my home network, but recognizes many of my neighbours’ networks. The home network auto connects as soon as I switch off flight/airplane mode, but then I get charged for voice calls even if I reject them. Any idea why airplane mode would cause my home network, auto connected in normal mode, to drop in airplane/flight WiFi mode?

If it's seeing your neighbors' wifi signals, it should see yours. I'd have the carrier check it (or replace it).