How could the pastor, televangelist etc. prove that she/she is telling the truth?
There was a news story about a business man who became convinced by his Baptist pastor to donate large to the church in order to benefit financially but then he became near bankrupt. Then he made a lawsuit against the church. However one of the well-to-do church members offered the guy a cash settlement to shut him up.
*It should be noted that the effort may be moot, because believers generally have little interest in proof or evidence, as they have even less interest in wanting to know what is really true. This is why they are believers.
Such a pastor can’t prove their own point, because there is no truth anywhere to support their assertions. I could spend columns of text debunking their fallacious holy book and his abuse of it’s tenets, but logic is not a notable strong suit among followers of such charlatans.
I don't think God can be bought.