In an environment where you can't trust them (phone support), you can tell them there might be dust on the connectors and ask them to unplug it and plug it back

In an environment where you can't trust them (phone support), you can tell them there might be dust on the connectors and ask them to unplug it and plug it back in again. Only when they go to do that, they realize it was never plugged in and they don't even have to admit they were lying.