Wireless problem with Charter

[RAult]

My cable connection to my iMac is through Charter. For the last few years I have used it as a router to connect to my MacBook wirelessly and it has worked beautifully. Having just returned from the winter in Florida, I find this no longer works. When I attempt to open my MacBook internet connection to my home screen, all I can get is a Charter screen or a message that "You are not connected to the internet." Airport is on and my MacBook shows that I am on the correct wireless connection. The Charter technician says that, since I am not using a Charter wireless router, she can't help me. This has never been a problem before. Has Charter changed something or what?