Hi, Marielrosario08.
I'm glad you decided to reach out on the Apple Support Communities. If I understand correctly, all the third-party apps that use a web-based call feature are experiencing an issue where the audio cuts out and you’re not able to be heard by the others on the call. It sounds like you can immediately switch to another app and the audio starts working there. Maybe I can help get to the bottom of the issue with you.
You mentioned that it only happens when you’re not a video call and that the audio works great when it’s audio only. In cases like this, and because it’s happening on more than one app, it’s usually a connection issue. It’s possible the combined video and audio is using more of your internet connection than your connection can handle. Have you tried switching between cellular data and Wi-Fi to see if it works better on one connection than the other?
If not, I would start there. It’s a good idea to restart your iPhone and your modem/router before you test. This will ensure the best connection.
Restart your iPhone - Apple Support
You also mentioned that they aren’t able to hear you. Are you able to hear them when this happens? If you can hear them, it may be a microphone issue. Try testing with your EarPods or another pair of headphones to see if it makes a difference. I would also make sure those apps have permission to access the Microphone on your device:
Change app access to information on iPhone - Apple Support
If you haven’t already, I would also make sure you’re on the latest iOS version.
Update your iPhone, iPad, or iPod touch - Apple Support
All my best.