Anyone know (and willing to share) what are they using for PSTN integration? I've been looking into options for our non-profit tech startup (Ameelio) and about

Anyone know (and willing to share) what are they using for PSTN integration? I've been looking into options for our non-profit tech startup (Ameelio) and about the best pricing I can find is about 1.35 cents per minute. It surprises (and saddens) me that it's still so expensive. I'm sure at a bigger scale you can negotiate better pricing, but based on the quick conversations I've had with vendors it doesn't get significantly cheaper.