If you have hard water (we do) don't soak them in saltwater - it makes it even less likely they will soften (in hard water) - instead try soaking them overnight, then rinse and add water to cover the top of the beans (at least an inch) now bring to a rapid boil, turn off and let sit for an hour to three or four hours.
After sitting in the hot water, you can either rinse again and add more water or just use the same water; bring it back up to a rapid boil and then simmer until soft.
Once SOFT add salt and other flavorings - you can add garlic/onion/chile to these beans before softening but not anything with salt in it like salsa.
After the final adding of ingredients, simmer them for an hour to over-night depending on what you are making.
I've been doing this for 25 years and our water here is so hard it almost stands up by itself (just kidding but you get the idea).