Foxtel problem

I have foxtel digital and recently its playing up. Like when I go to some channels, it will not get them, and no signal is displayed, but its intemitent, and not on all channels, but another day, the channel will come up straight away. I called foxtel, and they said if its a problem with my wiring I will be slugged a hefty callout fee. But I don't think it would be my wiring, because if it was it would be all the channels, not just some right ? I thought I would ask you guys first for advice. Cheers,