Page 72 of the user guide says this...
To reset some of the menu settings to their original values, select Menu > Settings > Restore factory settings. Enter the security code. The data you have entered or downloaded, such as names and phone
numbers saved in Contacts, are not deleted.
RECEPTION is another matter - the phone needs to be in a place where the signal strength is adequate and that will be more to do with the service provider than to do with the phone.