Which OS are you using? Do you have any other pc's that are connecting ok? Are your wireless and ethernet drivers up to date - check in Device Manager?
Some simple things to try.
I assume that, because your ISP advised you to change channel settings on the router, that this is a wireless connection. If so, have you tried to connect using an ethernet cable.
It could be that your router is not allocating an IP address to your PC. If you have just a router:-
Turn off all PC's, disconnect the power to the router and the router from the PC if you had an ethernet connection. Boot up a pc, restore power to your router. Connect the pc by ethernet to your router and wait.
If there is still no connection right click on your ethernet adapter, disable it and re-enable it.