Bluetooth headset the other party can't hear me on any internet calls

Hello Everyone,

I have iPhone 4S, I bought new bluetooth headset, it is working fine on normal calls, but when using it on internet calls like WhatsApp calls or Messenger calls etc… the other party can’t hear me but I hear him very well, and the Audio button is flickering between (Audio symbol with 3 brackets) and (Audio symbol with bluetooth logo) I have attached gif image showing the flickering.

Here is it

By the way, I bought another one, it worked for the first time but after charging it it makes the same problem.

Please help.

Thank you