There's no way you can do do opposing tones on two pins so that it uses two dc tones to make a single AC tone? That was an idea I had but I have no idea where to start that in a program.
Perhaps you can get an apparent ac, two exact square waves but 180 degrees out of phase
then between those pins you will get an apparent ac signal as the positive and negative sides flip flop
Basically you can get an h-bridge meant for a dc motor, and wire it to the coil instead,
you'll need to check if the h-bridge can be switched that fast
DC -> AC conversion is done using something called "Inverter". There are ICs that do this job quite easily, and the cost of the IC, apparently increases with the amount of current you want to put out.