It depends on what the OP is trying to do. By their original question, it might be that they are struggling with thin negatives and are looking to improve on that. Raising the iso will not increase negative density but would make them lighter, or, thinner. If the OP is looking to improve negative density, then either lowering the iso or increasing development time might work for them. The listed iso on a roll of film is just a starting point and should not be seen as gospel. The same goes for development time.
Experimenting with different iso settings and development times would make understanding the link between iso settings and how dark the negative is much easier to understand. I only develop b&w right now, so if the OP is asking the question in regards to color, the development time manipulation might not apply. I'm not familiar with the C-41 process and while the same principle would apply, I have no experience with it to allow comment on color.