Bizarre interference with calls ?

For the past few months, every time I have called my mom or sister out of country, I've received a ton of interference (crackly noises, etc.). In the past couple of weeks, my sister and mom can't hear me, but they can hear another person speaking (a couple of times it's been a man, a couple of times a woman). I can hear my mom/sister clearly, the other person can't seem to hear them, but they can't hear me and are hearing this other person instead of me. It's super weird. Any ideas what's causing this? I have Verizon and they both have Rogers.

Edited to say - any tips for getting through to someone at Verizon who can actually help/look into this? This is a massive privacy issue.