Weird Portable Wifi Q

my mother bought a portable wifi thingie for her car for the kids to use when driving around. When her car is parked at the kids' house, my nephew is having problems using his iPhone. He is saying he is having trouble connecting to the home router for wifi (it keeps toggling back and forth) and he's having bandwidth issues like getting texts but not seeing photo attachments. 

Can anyone make any sense of this?

Tell him to go on his iphone and choose "forget this network." It won't recognize Grandma's network anymore.

tried that and it didn't work. It's also happening after she leaves so he may not have been correct about the cause.

1) says he's connected to wifi/internet but he's not

2) can send or receive pictures in texts

Probably not the hotspot then. If it's forgotten, it won't connect to the device. Maybe suggest rebooting the router.

Get a 5GHz router. 

If it happens after she leaves, either it is not the problem or his device is still trying to connect to her wifi even though the source of the wifi is no longer there. Suggest that he go to settings and see which wifi connection his device is defaulting to now. He should select the wifi his device was connecting to before the problem started.