T and L have been thrown back to past. T has had his hometown ruined in the past (this is not brought up during the conversation explicitly) so L asks should they stop by it. T is for a moment unsure then this excahnge happens
L: そうなの…？ 過去を変えちゃうと、未来って変わっちゃうの？
The following is my a bit rough translation as of now.
T:But I don’t know. Because I’d hate it if future changed due to our knowing about past events or meddling in them.
L: Is that so? If you changed the past would future change?
T: No, I’m sure of it. Among other things, you and me wouldn’t have met.
I have two issues here. One is minor and other more major. First one is that I'm not sure, but I'm assuming that して in first line is probably meant to be a kind of soft if. Past events are known of and/or meddled in which then might cause changes in future. I'm not entirely sure if I'm right there.
The more major problem comes in the next line. It's the 未来って変わっちゃうの？ bit. I'm not sure what's って supposed to convey. It's usually some kind of quote or like, buuut...
Wait. An idea strikes me right now. Is that って a way to refer to the previous line, and it in turn means more that future that changed would be unpleasant. Basically it's a way to express
Would the (unpleasant) (changed) future you spoke of change?
Hmm. That's still not entirely right. I'm definitely not seeing something right.
So what do you think of this conundrum of mine?