it is not the tv card grabbing skype, it is skype using the tv card. In skype, under tools => options, there you will find your video settings as well as audio settings.
From a drop down under video, select your camera if you have one or select none. In audio, select you mic input instead of the tv tuners audio.
after selecting the proper devices / inputs, don't forget to "save" the settings at the bottom of the config page.