Hey Agustinapupe,
It sounds like you're having an issue with not hearing calls on your iPhone when using your Apple Watch. We can understand wanting to look into that further. We want to help.
This would be expected behavior. You can learn more about this here: Notifications on your Apple Watch
Notifications go to either your Apple Watch or iPhone, but not both. Learn when a notification might appear on your iPhone, instead of your Apple Watch, below.

If your iPhone is unlocked, you'll get notifications on your iPhone instead of your Apple Watch.

If your iPhone is locked or asleep, you'll get notifications on your Apple Watch, unless your Apple Watch is locked with your passcode."
Thanks!