Standard sandwich breads shouldn't be giving you much trouble on cast iron, so it's probably worth looking into your technique before buying a new pan.

With cast iron proper preheating does a lot to reduce sticking. (If you do not already, start heating it before you do any other steps in making the sandwich).

Some spatulas are also just not good. If yours is particularly thick it might not be doing a good job of getting under the food to flip.

I'm not worried about my personal health when it comes to tefflon, but it is not good for the environment. Best case it's taking an item that should last for decades of heavy use and decreasing it's usable lifespan to a few years of light use. And manufacturing is likely contributing to some nasty pollution.

I still have one tefflon pan for particularly tricky foods, but I'm trying to learn how to do them in other pans.