Hi @Soyloquete123, let me see if I can help out here.
I have translated your question to English as this is an International forum, please post any replies in English and it will be easier for me and other users to assist you.
So if I understand you correctly, you are not able to hear the counterpart when in a call? Have you been able to carry out a quick test of the speakers in the phone in order to see if the hardware works as intended? Find and tap Settings > Support > Xperia tests > Speakers & microphone.
Another thing that you can try is to reboot your phone in safe mode to see if the earspeaker works better there. All apps downloaded from Play store is temporarily deactivated while in safe mode and by doing this, you can see if this behaviour is caused by a downloaded app. For more information on safe mode and how to use it, click here.
If the earspeaker do not work in safe mode either, I would suggest that you try to repair the software on the phone using Xperia Companion and a computer. Keep in mind though that all user data will be erased by the repair, so it is advised to do a backup before to avoid data loss.
Try this and let me know how it goes, and please do elaborate if I have misinterpreted your question in any way!
