Greetings emylove,
Thanks for visiting the Apple Support Communities! I understand your Powerbeats3 aren't working while on a phone call or FaceTime call as expected, as you mentioned the other party isn't able to hear when you speak.
I suggest resetting your Beats, as described in the following guide: Set up and use your Powerbeats3 Wireless Earphones
To further isolate the behavior, I suggest testing the Beats with another audio source. Keep in mind, using the built-in remote and microphone with your Powerbeats3 is supported with Apple iOS devices, but varies with other brands and products, as mentioned in the following guide: Product Compatibility
If further assistance is needed, I suggest contacting Apple for support: Contact Apple Support
Cheers.