Audio issue

Hi smart intelligent people!

I have been trying for two days now. I'm in Europe trying to have a zoom call with someone in the USA. I can hear they, but they can't hear me. I'm using an android phone. I have tested with people in Europe and they can hear me perfectly fine. Any ideas or has someone had this issue? 

I appreciate any kind of feedback 😊

Could it be a phone issue and should work with a laptop? I'm out of town on vacation and haven't the laptop with me. Thanks!