I do not question that some people think they hear God talk to them. This may or may not be a mental condition like that of the "Son of Sam" who took orders from a dog.
I am sure that they are convinced of this. I have heard far too many goofy things from such people to take them seriously.
Prophet, however, is a different role. A Prophet is a person divinely instructed to listen to God and pass along His words. The Pope does not claim to be a prophet. Pontiff, as you say, means "bridge", but the way that works is that the Pope is considered infallible only on matters of doctrine and dogma. What this means is that if the Pope gets it wrong, God will understand the sincerity of those who took the Pope's advise and not punish them for following the directive. If this sounds like a lot of mumbo-jumbo, you are right, it is. The Church has rather a lot of mumbo-jumbo like this. My favorite is their claim that the Song of Songs is not werotic poetry at all, it is a dialogue between Jesus and the Church. The Church has symmetric breasts and wonderful creamy thighs. oooooo yeah!