Does the band under the breast curl up if you have a tummy?

It does a little, but not that bad.

How do you determine the correct size?

I usually go to the manufacturer website and look for their size chart. Then I use a tape measure to measure the person the item is for. I order one of the items in what I think is the correct size. If it fits when I get it I order more if needed. If it doesn’t fit I take advantage of Amazon Primes free returns.

The delivery is taking forever. Is there any way to contact seller?

When I got my second order it took awhile, due to supply line issues with covid. My order finally arrived after about three weeks. Nothing serious, just a bit of a wait was all

I'm between sizes, either could work. Do these keep form or stretch with wear and washing?

I wasn’t sure what size to get so I bought two to try. Neither worked and they wouldn’t let me return. So I’m stuck with two bras that I can’t wear. Don’t recommend.