Is it possible to 'choose to believe' something?
Now that I think of it, I think so. Belief is accepting something is true without support. So, you can believe you can fly and that belief is fine but it's not backed up by the fact gravity "says" otherwise. In religion, it works differently. You can believe or accept something supernatural is true without support, just as you can believe you can fly. Though, one is a bit more dangerous than the other. So, it's possible. As for beneficial, it depends on the religion and how you adhere to it.
In other words, is belief a choice? or are you simply convinced/unconvinced by what you have learned so far?
I'm convinced in what I've learned so far because my experiences lead me to conclude my beliefs are true. Since they are beliefs (many of them aren't supported just personal biases), I tend not to think about it too much in those regards. Unless that bias (being convinced) is causing harm to self and others, I don't see it an issue.
Also, it is certainly possible to act 'as if' something is true. But is that the same as belief? Or merely a provisional assumption until more evidence is found?
Yes. Belief, I believe, is something mental. You can act like it's true (jump off a bridge to fly) but doesn't make it so. The belief itself isn't the issue just as hearing voices in itself isn't the issue. It's what people do because of their beliefs or what their voices tell them that "may" be the issue. The action and belief in itself is fine.
If I waited for evidence for every thing I experienced, I'd be skeptical all my life and never try anything new. I'm not sure about other countries, but it seems America has a bit of skepticism. That or I'm just generalizing since a lot of Americans are christians.
Choosing to believe or accept something is true, to me, isn't really the issue. Evidence doesn't matter unless you're talking about, say, medical field and other important areas of study. Though, I do believe some believers tend to try and find evidence for their religion (i.e. saying the existence of where jesus rested means jesus miracles are true) but I'm sure not all religions need that for their belief to be true and accept it without regards of objective evidence.