Pics, please.

Without seeing a photo, it sounds like you should ask for a re-do (which means a new slab, hopefully one that suits you will be available!) Because of the not-perpendicular cut more than anything.

Thanks, I think that a new slab will be a starting point. What also might work is trimming the stone so that the sink sits below with a very small (1/8-1/4 inch) and uniform border all around. We saw a picture like that and it didn't look bad. Here's a picture of the worst corner--its pretty easy to see how bad the edge and corner is. I think it might have been bring your child to work day at the slab yard.

Red:

Your sink should be dropped, the cutout remade square and with a perfect slight positive reveal, then profiled and polished in place. One guy from my crew could do it in 6 hours with no mess, but we're exceptionally good at this.

We'd throw in a sink refinish too.