I don't really know. It could be a true story that's been embellished for dramatic effect, or it could be entirely fictional. Without more information, it's difficult to tell.
I'm pretty sure 'Prayer Never Fails' is not based on a true story. It might draw inspiration from various sources but doesn't directly stem from real-life incidents.
One example could be a person who was seriously ill. The doctors had given little hope. But through constant prayer, the person's condition started to improve mysteriously. It was as if a higher power was at work.
Well, it could be inspired by real events but might have been embellished or changed for dramatic effect. Not everything presented might be strictly factual.