Adverts even though I have premium service and am logged in.

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Hi yesterday I was live streaming a little show on my ITVfest channel. I was logged in to 2 computers on 2 different networks. One was to broadcast the show and the other was to monitor.
The monitor computer stream had adverts on it, even though I pay for premium service so that this doesn't happen. It was really frustrating and did not give a good impression to those i was working with. Can you tell me why it happened and if there's anything that can be done to prevent it happening in the future?
Best Wishes,

Mark