I know that causative verb form + てもらう means to let somebody do something. And てもいいですか is for asking for permission. But I don't quite understand the use of these 2 constructions together.
If I wanted to ask someone to let me use their phone, I would possibly say:
How are the meanings of the two sentences different? Is "電話を使わせてもらってもいいですか" just more polite?