Ok, after a few hours of research I finally found a couple of solutions.
1) probably the cheapest method is to purchase an app called soundabout pro for 2.99. It lets you prioritize bluetooth over headphone when receiving calls. They have a free version, but it disables the feature that we need. Maybe there are free apps similar to this, but I haven't been able to find it.
2) to purchase a bt dongle that connects to aux, this is more expensive and doesn't seem to work so well. You have to keep pairing it everytime and also make sure the dongle is charged somehow.
3) Not really a solution, but a work around, is just not use bt and answer calls thru your phone. But drawkback is you have to hold your phone and speak into mic and you can hear the other person via car speakers. This is what k normally do. Of course you lose your k. Car bt features too.
I will probably try that app out and see if it works. Because I don't want to hold this phone to my mouth. Illegal here in cali, plus it is too noticeable when holding. I can't hide it in my hand lol.