Hello monicaxoxo,
Thanks for asking the Apple Support Communities for help with your iPhone and connectivity issues. Thanks for also mentioning the troubleshooting you have tried.
Since you have restored to factory and then restored your backup and the issue continues, the next step it to check if the problem is saved in the backup and dragged back in when you restore.
To test, try restoring the device to factory settings using your computer, and not restoring any backups. Before erasing your device, ensure you have a recent backup in iCloud or your computer. How to back up your iPhone, iPad, and iPod touch - Apple Support
Use your computer to restore your device to install a fresh version of iOS. This help article will assist you to complete these step: Restore your iPhone, iPad or iPod touch to factory settings - Apple Support
Once erased, ensure you set the device up as new, and do not restore any information from an iCloud or iTunes backup yet. This step will isolate the issue and let us know if it is related to the previous data or iOS on the device. Once the device is set up as new, you will test to see if the issues are still occurring. If this issue is no longer happening, we know the issue was with some data on the device or in the iOS version, which will most likely be saved in your backups. You can manually bring data back using iCloud or iTunes, but do not restore from the backup as you may bring the problem right back in. Once you log back in to iCloud with the same Apple ID that you used previously, all your data saved in iCloud will start repopulating on the device.
This help article has the info to help you get your other data back to your device, whether you have a Mac or a PC. Depending on the info, you may need to use File Sharing with iTunes or Finder mentioned here: Use iTunes to share files between your computer and your iOS or iPadOS device - Apple Support
You can also redownload fresh copies all of your previous purchases using this article: Redownload apps, music, movies, TV shows, and books - Apple Support
Thanks and have a great rest of your day.
