Echo in communication

Hello there, I’M french and not really skilly in phones (je ne suis pas informaticienne). There is quite often an echo in my communications. Not for me but for my partner. I have never experienced this with the actual sim card on my googled-smartphone, that I don’t use for 10 days now.
Do you have a lead…?? Could it be the Gigaset phone or something else?
Thanks for your answers!
MG

I can confirm this behaviour. In my case I can hear my self when connected to Car communication during phone calls.

maybe related to Echo on the car Bluetooth

Thank you.
Just to be precise: I have tried the Gigaset with another sim card (another provider) and the problem was still there. So I send it back. It seems that there is something with this phone about the echo.
Have a good day!