We have a two story home that is about 3800 square feet. The modem and router are located in an upstairs office. Wifi has no problem connecting to my MAC laptop all over the house however it won't connect to any mobile device like an iPad or iPhone. The problem arises more so downstairs than upstairs. The internet company says it isn't their problem because the modem works properly and at the correct speed. How do I get the internet to work all over the house. We have tried range extenders and they do not work.